TN295 




No. 9024 








"oV 








^oV 




4> N<> 




J'S^V* %^^V* X'^'V^ ^^^y^.X^^'V^ %/^v 




> A^V - ^fijl^ o A>^ o%7WW?" A*Cf> 






* v I 




V *o„o» <^ 

* ,£** j lliilr o ^^ 




:. ^ ^ ' »w^. ^ >" 






A* V *V 




^A* - 




> AT 



• » " ^ ^o, *7 b XT* A <v» 




° 4 .-*-,-'%p 9 v^^\/ %^-\* Q .. V'^V* \. V^' o* .... ^ ' 








- ^!a a^ * 



*w 














SWA V 





















P* .*l^. ^°o 







^°^ :i jP^ -. Q ^^,* <5°^ 




> . 1 • • . *>n rt v , , , 



% •: 










> 5 * * • . Cv v . » 








^0* 










ik-.%^'.-aK\xy ••- 







<^v 






w 



« v '<u - • - • " 




f* # °' *>■ V .*!» 












n* . « • 



^> '= . » • A <A 



4? . 








-1 o>. 




£ 










* • 



. «? # *yMsp* av < «o, «? ^ 




Bureau of Mines Information Circular/1985 



Feasibility of Water Diversion 
and Overburden Dewatering 

By Noel N. Moebs and Michael L. Clar 




UNITED STATES DEPARTMENT OF THE INTERIOR 



75 

*f/NES 75TH AV 5 ^ 



Information Circular 9024 
n 



Feasibility of Water Diversion 
and Overburden Dewatering 

By Noel N. Moebs and Michael L. Clar 




UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 




I 



As the Nation's principal conservation agency, the Department of the Interior 
has responsibility for most of our nationally owned public lands and natural 
resources. This includes fostering the wisest use of our land and water re- 
sources, protecting our fish and wildlife, preserving the environmental and 
cultural values of our national parks and historical places, and providing for 
the enjoyment of life through outdoor recreation. The Department assesses 
our energy and mineral resources and works to assure that their development is 
in the best interests of all our people. Thg*«ftSB3cTOe»i also has a major re- 
sponsibility for American Indian reseryrf^&£ommunira£i\ind for people who 
live in Island Territories under U.S. 




Library of Congress Cataloging in Publication Data: 



Moebs, Noel N 

Feasibility of water diversion and overburden dewatering. 

(Information circular / United States Department of the Interior, 
Bureau of Mines ; 9024) 

Bibliography: p. 47-49. 

Supt. of Docs, no.: I 28.27:9024. 

1. Mine drainage. 2. Mine water. 3. Coal mines and mining- 
Appalachian Region. I. Gar, Michael L. II. Title. III. Series: In- 
formation circular (United States. Bureau of Mines) ; 9024. 



TN295.U4 [TN321] 622s [622'. 334] 84-600364 



n 



\3 



o-S CONTENTS 



£^ Page 

c 

Abstract 1 

Introduction 2 

Acknowledgments 4 

Impacts of mine water 4 

Health and safety 4 

Production 6 

Environment 6 

Costs 7 

Sources of inflow to underground mines 8 

Ba ckg round 8 

Water entrance into mines 9 

Coal and water-bearing strata 10 

Water in shallow mines 13 

Surface seepage 13 

Surface water inrush 14 

Water entrance through fractures 15 

Joints 16 

Faults and fracture zones 16 

Mine subsidence fractures * 17 

Abandoned deep mines 18 

Barrier pillars 18 

Interconnections 19 

Boreholes, wells, and shafts 20 

Water control practices 21 

Siting surface facilities and openings 22 

Surface runoff diversion 22 

Surface regrading 22 

Soil sealing 24 

Stream channel modifications 24 

Grouting 25 

Borehole sealing 25 

Subsurface soil sealing 26 

Mine sealing 27 

Well dewatering 28 

Ground water pumping directly to the surface 29 

Gravity drainage to the mine 29 

Gravity drainage into lower aquifers 30 

Costs 31 

Case study 32 

Summary of water control practices 32 

Analysis of three water control projects 33 

Technical effectiveness 38 

Case study 1 38 

Case study 2 41 

Case study 3 41 

Costs 42 

Case study 1 42 

*OCase study 2 42 

Case study 3 42 

5 

— : 



11 



CONTENTS— Continued 

Page 

Other considerations 43 

Conclusions 44 

Impacts of mine water 44 

Sources of inflow to underground mines 45 

Water control methods 45 

Current engineering practices 45 

Recommendations 46 

References 47 

Appendix A. — Case study 1 50 

Appendix 8. — Case study 2 60 

Appendix C . — Case study 3 66 

ILLUSTRATIONS 

1 . Summary of cost analysis 7 

2. Matrix of mine water controls versus mine water sources 21 

3 . Ground water pumping systems 30 

4 . Gravity drainage into mine 30 

5. Gravity drainage into underlying aquifers 31 

6. Map of Nemacolin Mine 41 

A-l. Location map of Lancashire No. 20 Mine and pilot well dewatering site.... 50 

A-2. Generalized stratigraphic column, case study 1 51 

A- 3 . Water transport system 54 

A-4 . Average daily flows to treatment plant 54 

A- 5 . Main G study area 55 

A-6 . Average mine inflow in Main G study area 56 

A-7. Location map of dewatering and observation wells 56 

A-8. Average daily mine inflow, July 1977 57 

A-9. Average daily mine inflow, September 197 7 58 

B-l . Planned and ongoing mine operations 60 

B-2. Generalized stratigraphic column, case study 2 61 

B-3. Site cross section 62 

TABLES 

1. Relationship between mine depth and well dewatering 7 

2. Representative costs for surface regrading and restoring 24 

3. Representative costs for constructing various types of mine seals 29 

4. Summary of water control practices 34 

5. Summary of water control costs 36 

6. Comparison of geologic conditions at three case study sites 39 

7. Comparison of hydrologic conditions at three case study sites 40 

B-l . Beaver Run inflows 64 

B-2 . Gobbler ' s Knob inf lows 64 

B-3. Big George inflows 65 





UNIT OF MEASURE ABBREVIATIONS 


USED IN THIS 


REPORT 


cm 


centimeter 






km 


kilometer 


cm 2 /s 


square 


centimeter per second 


km 2 


square kilometer 


ft 


foot 








L 


liter 


ft 2 


square 


foot 






lb/in 2 


pound per square inch 


ft 3 


cubic foot 






lb/ton 


pound per ton 


ft 3 /s 


cubic i 


:oot per 


second 




L/d 


liter per day 


gal 


gallon 








L/s 


liter per second 


gpd 


gallon 


per day 






m 


meter 


gpd/ft 


gallon 


per day 


per foot 




m 3 


cubic meter 


gpd/ft 2 


gallon 


per day 


per square 


foot 


mg/L 


milligram' per liter 


gpd/mi 2 


gallon 


per day 


per square 


mile 


mi 2 


square mile 


gpm 


gallon 


per minute 




pet 


percent 


h 


hour 








ppm 


part per million 


hp 


horsep< 


Dwer 






t 


metric ton 


in 


inch 








ton/yr 


ton per year 


in/h 


inch p 


ar hour 






tpy 


metric ton per year 


kg/m 2 


kilogram per square meter 




yd 3 


cubic yard 


kg/t 


kilogram per metric ton 




yr 


year 



FEASIBILITY OF WATER DIVERSION AND OVERBURDEN DEWATERING 

By Noel N. Moebs and Michael L. Clar 



ABSTRACT 

The Bureau of Mines studied the feasibility of water diversion and 
overburden dewatering for underground coal mines in the Appalachian re- 
gion. All relevant published literature pertaining to the occurrence 
and control of surface and ground water in underground coal mines was 
reviewed, and the impacts of mine water with respect to health and 
safety, production, environment, and costs were assessed and are de- 
scribed in this report. The report also identifies the sources of wa- 
ter inflow into underground coal mines, and gives a summary description 
and evaluation of techniques that can be used to reduce the amount of 
water entering these mines. Engineering practices currently used by 
operating coal mines in the Appalachian region to prevent the movement 
of ground and surface water into active coal workings were reviewed 
and are summarized. Major emphasis has been placed on the identifica- 
tion of geologic and hydrologic conditions of the site, the water con- 
trol methods used, and an evaluation of their technical and cost 
effectiveness. 



geologist, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
^vice president, Hydro-Terra, Inc., Columbia, MD . 



INTRODUCTION 



This report presents the results of a 
study undertaken by the Bureau of Mines 
to determine the feasibility of water 
diversion and overburden dewatering tech- 
niques in advance of underground coal 
mining operations in the Appalachian coal 
districts. 

The presence and, in particular, the 
ponding of water in the active workings 
of underground coal mines can be very 
detrimental to health and safety, produc- 
tion, costs, and the environment. The 
negative impacts that a wet mine has 
in these areas are generally well recog- 
nized. However, there exists no com- 
prehensive and quantitative reporting 
of these impacts in the published 
literature. 

In the Appalachian coal districts, 
where major underground mine expansions 
are anticipated, drainage in the coal 
mines is extremely variable. The volume 
of water to be handled, which is typical- 
ly expressed in terms of tons of water 
pumped out of the mine for every ton of 
coal mined, can range from an average of 
5 tons in the Pennsylvania bituminous 
mines to 36 tons in the anthracite 
region. 

Several approaches have been proposed 
either to dewater the mine area in ad- 
vance of mining or to substantially re- 
duce the amount of water reaching the 
mine area by diverting or reducing the 
infiltration of surface waters. Many of 
these methods, however, address hypothet- 
ical conditions rather than actual situ- 
ations. Some of the literature treats 
special situations such as preventing wa- 
ter from entering through boreholes, sub- 
sided or stripped areas, or surface 
streams entering through old mine open- 
ings. Some researchers have addressed 
water diversion and well dewatering tech- 
niques as control measures and proposed 
routing and rechanneling of surface flow 
as an effective method of excluding water 
from mines. 

Although the methodology for imple- 
menting these approaches is not new, to 
date both the application and the success 



of these methods in underground coal 
mines have been limited. Consequently, 
these methods have not found widespread 
use in the coal industry in the United 
States. The most common approach to 
handling water in underground mines con- 
sists of collecting the water by gravity 
and pumping the water back out to the 
surface where treatment is provided if 
needed, prior to discharging to the re- 
ceiving streams. 

The still recent Surface Mining Control 
and Reclamation Act (SMCRA) and the ensu- 
ing permanent regulatory program of the 
Office of Surface Mining (OSM) represent 
an additional consideration. Several 
general requirements are stipulated that 
are related to the effects of underground 
coal mining activities on the hydrologic 
balance: 

Section 817.41 Hydrologic Balance: 
General Requirements 3 

(a) Underground mining activities 
shall be planned and conducted to 
minimize changes to the prevailing 
hydrologic balance in both the mine 
plan and adjacent areas, in or- 
der to prevent long-term adverse 
changes in that balance that could 
result from those activities. 

(b) Changes in water quality and 
quantity, in the depth to ground 
water, and in the location of sur- 
face water drainage channels shall 
be minimized so that the approved 
postmining land use of the permit 
area is not adversely affected. 

(c) In no case shall Federal 
and State water quality statutes, 

^U.S. Code of Federal Regulations. Ti- 
tle 30 — Mineral Resources; Chapter VII-- 
Office of Surface Mining Reclamation and 
Enforcement, Department of the Interior; 
Subchapter K--Permanent Program Perform- 
ance Standards; Part 81 7--Underground 
Mining Activities; July 1, 1981. 



regulations , standards or effluent 
limitations be violated. 

(d) Operations shall be conducted 
to minimize water pollution and, 
where necessary, treatment methods 
shall be used to control water 
pollution. 

(1) Each person who conducts un- 
derground mining activities shall 
emphasize mining and reclamation 
practices that prevent or minimize 
water pollution. Changes in flow 
shall be used in preference to the 
use of water treatment facilities. 

(2) Acceptable practices to con- 
trol and minimize water pollution 
include, but are not limited to — 

(i) Stabilizing disturbed areas 
through land shaping; 

(ii) Diverting runoff; 

(iii) Achieving quickly germinat- 
ing and growing stands of temporary 
vegetation; 

(iv) Regulating channel velocity 
of water; 

(v) Lining drainage channels with 
rock or vegetation; 

(vi) Mulching; 

(vii) Selectively placing and 
sealing acid-forming and toxic- 
forming materials; 

(viii) Designing mines to prevent 
gravity drainage of acid waters; 

(ix) Sealing; 

(x) Controlling subsidence; and 

(xi) Preventing acid mine 
drainage. 

(3) If the practices listed at 
paragraph (d)(2) of this section 



are not adequate to meet the 
requirements of this part, the per- 
son who conducts underground mining 
activities shall operate and main- 
tain the necessary water treatment 
facilities for as long as treatment 
is required under this part. 

As the above clearly indicates, any 
method proposed for use must include a 
thorough assessment of the impact it may 
produce on the hydrologic balance of the 
mine site and will require the approval 
of this new regulatory agency (OSM) or 
the appropriate State agency. 

The combined concerns for environmental 
protection and for a safe and productive 
workplace demand additional studies and 
research on the feasibility of water di- 
version and overburden dewatering to ad- 
vance the state of the art. The perform- 
ance characteristics of 'these methods 
need to be evaluated and documented. It 
is unlikely that widespread use of such 
methods will occur until sound quanti- 
tative data that justify their use are 
presented. 

This Bureau research project was under- 
taken to study the feasibility of water 
diversion and overburden dewatering in 
advance of mining in underground coal 
mines in the Appalachian coal districts. 
This basic objective was accomplished 
through — 

1. A review of the literature relative 
to preventing surface or shallow ground 
water from entering underground coal 
mines. The literature evaluation focused 
on three major areas: (1) the impacts of 
mine water, (2) sources of water inflow 
to underground mines, and (3) available 
water control practices. 

2. An on-site review and analysis of 
current engineering practices. Three in- 
dividual case studies are presented in 
appendixes A, B, and C. 

The combined results of the literature 
evaluation and on-site review are summa- 
rized in this report. 



ACKNOWLEDGMENTS 



The authors are grateful for the coop- 
eration of numerous coal mining companies 
who contributed information for this 
study. In particular, the authors wish 
to thank the Barnes and Tucker Co. , Jones 
and Laughlin Steel Corp. , and Mettiki 
Coal Corp. , for information used in com- 
piling the case studies. John J. Ferran- 
dino and Connie Bosma of Hittman Associ- 
ates, Inc. , contributed substantially to 
the text and data collection. 



Figures A-3, A-4, A-5, A-6, A-7, A-8, 
and A- 9 were adapted from illustrations 
by W. A. Wahler in "Dewatering Active 
Underground Coal Mines: Technical As- 
pects and Cost Ef f eciveness" (38) . 4 Fig- 
ures 3, 4, and 5 were adapted from il- 
lustrations by H. L. Lovell and J. W. 
Gunnett in "Hydrological Influences in 
Preventative Control of Mine Drainage 
From Deep Coal Mining" (19). 



IMPACTS OF MINE WATER 



An understanding and a quantification 
of the extent to which water can bene- 
fit or impede underground coal mining 
operations is a prerequisite to conduct- 
ing an assessment of the effectiveness 
of available water control practices. 
For the purposes of this study, the ef- 
fects of mine water have been organized 
into four categories: (1) health and 
safety, (2) production, (3) environment, 
and (4) costs. 

Most recent publications underemphasize 
the health, safety, and productivity 
problems associated with water in under- 
ground mines, and instead focus on the 
environmental effects of mine water. In 
underground mines in the Pennsylvania 
anthracite region, 36 tons of water are 
pumped out of the mine for every ton 
of coal mined. In the bituminous coal 
mines , this average is between 5 and 6 
tons of water for every ton of coal. 

Regardless of the water source, the de- 
terminants of the water problems in a 
mine are (1) the rate of inflow, (2) the 
mode and location of inflow, and (3) pro- 
visions to handle the inflow. A uniform 
rate of inflow will not normally present 
severe problems in designing a pumping 
plant. However, unforeseen high inflow 
rates have the potential to cause major 
disruptions in normal activities. 

Water seeping into the mine at loca- 
tions far removed from the active work- 
ings can be directed to suitable sumps 
and pumped out of the mine. When the in- 
flow is in the active workings and is a 
slow seepage, the water can be allowed to 
accumulate and can then be pumped out to 



a section sump using portable pumps. Wa- 
ter problems tend to become critical when 
high inflow rates are generated in ac- 
tive workings by the advance of the work 
itself. 

HEALTH AND SAFETY 

In defining the significant effects 
of water on health and safety in the 
workplace, the following factors must 
be considered: (1) inrushes of water, 
(2) ventilation, (3) roof conditions, 
(4) maintenance problems, (5) corrosion, 
and (6) miscellaneous effects. 

Inrushes of Water . - The Appalachian 
coal districts are the oldest coal mining 
districts in the country. New mines in 
these districts are often adjacent to 
and/or below older abandoned mines. 
Since these older abandoned mines are of- 
ten flooded, they behave as underground 
water reservoirs, and the potential for 
inrushes of water must be considered in 
siting new mines. This concern is likely 
to increase in the future as the number 
of new mines grows, particularly since 
these new mines will often be sited in 
the deeper seams underlying the older wa- 
terlogged workings. The Bureau has de- 
veloped guidelines to prevent and control 
the inrush of mine waters. These guide- 
lines include the work by Wardell ( 40 ) 
and Skelly and Loy (32). 



^Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding the appendixes. 



Ventilation . - Water can affect a 
mine's ventilation in three ways: It can 
aggravate the heat and humidity problem, 
increase the methane emission, and block, 
the ventilating airways. 

Roof Conditions. - Several studies have 
been performed on the influence of humid- 
ity on roofs in underground mines. These 
studies indicate that roofs composed of 
soft shales or some form of clay, with 
mud partings , are most vulnerable to 
failure. Sometimes an effort is made to 
recover an upper seam that was not mined 
before a lower seam was extracted. In 
this case, the subsidence in the overly- 
ing strata, as a result of the lower seam 
mining, can cause roof control problems. 
Cracks and fissures in the broken strata 
may be filled with mud and clay. When 
the upper seam is developed for mining, 
water tends to wash into these fillings 
and create weakened roof conditions. Wa- 
ter seeping through strata is indicative 
of poor strata conditions. 

Roof collapses are often associated 
with the presence of water in conjunction 
with geologic unconformities. Water will 
act as a lubricant to decrease frictional 
resistance to movement of rock strata. 
Lubrication of a slip surface, such as a 
slickenside, requires only small volumes 
of water or moisture, although the pre- 
cise amount has yet to be quantified. It 
is known, however, that the moisture sup- 
plied by the mine ventilation system is 
sufficient to cause failure in weak shale 
roofs. 

Maintenance Problems . - Water in mines 
creates special problems in the operation 
of electrical equipment. Whereas perma- 
nently located electrical equipment can 
be adequately protected from water, mo- 
bile equipment cannot be so easily pro- 
tected. Trailing cables and trolley 
wires are of greatest concern from a 
safety point of view. Defective splices 
and breaks in the insulation of cables 
have been responsible for severe shocks 
and burns [Mason ( 21_) ] . Trailing cables 
of all types are used at or near the coal 
face, where they are most likely to be 
damaged. Trailing cables are continually 
being handled, in many cases under wet 
conditions; therefore, there is always 



the danger of electrical shocks should a 
fault arise. 

Water tends to carry dirt and clay 
into exposed bearings, sockets, conveyor 
chains, and other machinery parts, in- 
creasing the frictional resistance to 
movement. In addition to the increased 
wear and tear, this can result in exces- 
sive heat generation. If unattended for 
long periods of time, the frictional heat 
can cause a fire. 

Corrosion . - Although most corrosion of 
mining equipment is minor, serious cor- 
rosion can occur under certain circum- 
stances. This problem is discussed in 
detail in papers by White (4_1_) and Kenny 
( 16) . According to White, mine water can 
be classified as follows: 

Type pH 

1— Highly acid i 1.5- 4.5 

2 — Soft, slightly acid 5.0- 7.0 

3 — Hard, neutral to alkaline... 7.0- 8.5 

4 — Soft, alkaline 7.5-11.0 

5 — Highly saline 6-9 

6 — Soft, acid 3.5- 5.5 

In laboratory tests, it was found that 
water fitting the description of types 1 
and 5 causes corrosion. Type 1 water is 
most corrosive because of the free sul- 
furic acid and ferric ions. Usually py- 
rite in the coal seams is the source for 
this water. Type 5 water contains a high 
concentration of dissolved salts, partic- 
ularly sodium chloride. The salt may 
come from the strata and is highly corro- 
sive as a result of the high electrical 
conductivity and of the interference to 
the rust-forming process. 

Miscellaneous Effects . - The accumula- 
tion of water in the mine makes it un- 
pleasant to work, and cuts down on work 
time and efficiency. More importantly, 
it may lead to an Increase in accidents. 

Although dangers from water account for 
a relatively small portion of accidents 
resulting in injuries and deaths, there 



is always the possibility of serious dis- 
asters when mining activity is in the 
vicinity of large bodies of water. Even 
if the existence of a water body is 
known, its exact location and the volume 
and head of water are usually not well 
defined. 

Owing to the variety of problems that 
can occur, it is impossible to form one 
set of rules that can be uniformly ap- 
plied in all cases. However, there are 
several general preventive measures that 
must be taken: 

• The potential water danger must be 
studied and surveyed on a mine site, 
area, and regional basis to assess the 
full extent of the danger. 

• Adequate sumps and gravity flow 
paths into them should be established as 
early as possible. 

• A plan must be formulated to ensure 
that workers are withdrawn safely in the 
event of an inrush. 

PRODUCTION 

The productivity of a mining system has 
been expressed as a function of a number 
of major independent variables [Stefanko 
(34) , Manula, Bouillot, Rivell, and Sand- 
ford (_20), Suboleski ( _35) ] . Excluding 
the mechanical equipment and the human 
element, these independent variables in- 
clude (1) roof quality, (2) methane lib- 
eration, (3) bottom quality, (4) water, 
(5) grades, (6) hardness and strength of 
seam, (7) seam height, and (8) depth of 
seam. 

To some extent these all are interre- 
lated with the presence of water; howev- 
er, each can also be a factor independent 
of others — for example, the roof may sim- 
ply be weak and the floor may have little 
bearing strength even when dry. 

ENVIRONMENT 

Underground coal mines can have an im- 
pact on both the quantity and quality of 
surface and ground waters. The impact 
on water quality has long been recognized 
and regulated by both State and Federal 



agencies. These regulations generally 
require that mine waters be treated to 
neutralize and remove pollutants prior to 
discharge to receiving streams. Conse- 
quently, some information is available 
related to the technology of controlling 
this impact. 

All of the water pumped from the mine 
will generally require treatment. A num- 
ber of dewatering schemes have been pro- 
posed based on the assumption that by 
intercepting the ground water before it 
contacts the mining operation, the re- 
quirement for treatment and the related 
cost could be avoided. 

The impacts of underground coal mines 
on water quantity can be short term or 
long term and can occur both during ac- 
tive mining and after abandonment. The 
two most noticeable and immediate impacts 
are changes in water levels and ground 
water flow. Lowering of the water table 
level or a decrease in ground water flow 
can result in the dewatering of shal- 
low wells and the loss of ground water 
supplies. 

The mechanisms that cause these hydro- 
logic impacts include (1) the removal of 
the coal seam, resulting in underground 
cavities that serve as broad sinks or un- 
derdrains , which receive ground water 
percolating downward from overlying 
strata, (2) the fracturing and separation 
of overlying strata resulting from the 
removal of the coal seam, and (3) the re- 
moval of the water from the mine by grav- 
ity drainage in jthe case of updip drift 
mining or by pumping in downdip drift, 
slope, or shaft mining. 

It must be pointed out that use of a 
dewatering technique will also result in 
changes (lowering) of water levels and 
will reduce ground water flows. Thus, 
the same type of hydrologic impacts will 
be experienced during mining. The dewa- 
tering techniques will not prevent the 
development of the mechanisms discussed 
above. Consequently, the hydrologic im- 
pacts will continue to be experienced af- 
ter the mining operation is completed. 

A recent investigation suggests that 
the hydrologic impacts of underground 
mines may be less severe in the future. 
An inventory of water levels in domestic 
wells in Marion County, WV, showed that 



TABLE 1. - Relationship between mine 
depth and well dewatering 



Mine depth, 
Ft 



Effect on wells completed 
above mining zone 



<200 All wells permanently 

dewatered. 
200 to 250.... Most wells permanently 

dewatered. 
250 to 300.... Some wells occasionally 

dewatered. 
>300 No wells dewatered. 



Source: 
(30). 



Sgambat, Labella, and Roebuck 



variations in long-term dewatering are 
related to mine depth [Rauch {21) ] . A 
similar investigation (table 1) found 
that when the mine depth exceeded 300 ft 
(91 m) , no wells completed above the min- 
ing zone were dewatered. A recent survey 
of 325 operating sections in Appalachia 
revealed that 92 pet of the surveyed sec- 
tions were 300 ft (91 m) deep or more. 
The average depth was 600 ft (183 m) , and 
the most frequently reported depth was 
500 ft (152 m) . These data suggest that 
dewatering of wells by underground mines 
may not be a frequent occurrence in the 
future. 

COSTS 

Mine water can affect mining costs in 
both direct and indirect ways. The di- 
rect costs associated with mine water in- 
clude costs for — 

• Water handling (collection, treat- 
ment, and disposal). 

• Coal preparation (additional costs). 

• Miscellaneous wet and waterproof pay 
items (such as blasting agents) . 

The indirect costs include — 

• Additional costs of time lost owing 
to health and safety aspects: venti- 
lation, floods and inrushes, and roof 
support. 



• Productivity losses. 

• Cost associated with additional 
maintenance requirements. 

The literature review revealed that 
there is very little information avail- 
able on the direct costs associated with 
mine water and even less on the indirect 
costs. Mining companies do not normally 
separate water-related costs from other 
costs in much detail. To date, water 
treatment costs are the only direct cost 
that has been thoroughly investigated. 
(The available data on water treatment 
costs are too extensive to summarize in 
this report, but selected references were 
reviewed and are given in the reference 
list at the end of this report.) 

Figure 1 presents a comprehensive sum- 
mary of water-handling costs experi- 
enced by an underground mine in central 




FIGURE 1. - Summary of cost analysis of water 
handling at one mine (38). 



Pennsylvania and serves to illustrate the 
major cost components (38) « The water- 
handling costs for this mine were gener- 
ated as part of a study to evaluate the 
effectiveness of dewatering an active 
mine from the surface, which represents a 
rare situation where cost data have been 
reported. The practicality of establish- 
ing standard figures for the industry is 
questionable because of the great varia- 
tion in physical factors such as depth, 
water quality, size of mine, geology, and 
engineering methods. However, examina- 
tion of costs incurred by mines within 
local mining districts operating in the 
same coal seam might yield useful plan- 
ning guidelines. 

Information on the indirect costs of 
mine water was very scarce. The indi- 
rect costs associated with the effects of 
mine water on health and safety and with 



additional maintenance requirements have 
yet to be quantified. A partial assess- 
ment of the indirect cost resulting from 
the impact of mine water on production 
can be generated based on the work of 
Suboleski (35). 

According to Suboleski, a reduction in 
the range of 32 to 50 tons (29 to 45 t) 
of coal per shift might be experienced 
between a mining section with a dry, hard 
floor and a section with a wet, rutted, 
and slippery floor. Assuming that the 
section operates three shifts per day, 
and 220 days per year, a decrease in pro- 
duction ranging from 21,120 to 33,000 
ton/yr (18,000 to 29,700 tpy) per section 
would result. Assuming a selling price 
of $20 per ton, a potential production 
loss ranging from $422,400 to $660,000 
annually per section would be suffered. 



SOURCES OF INFLOW TO UNDERGROUND MINES 



BACKGROUND 

Problems associated with water inflow 
into underground coal mines have an im- 
portant effect on the cost and progress 
of the mining operations. Greater knowl- 
edge and increased efficiency in reducing 
the risk of sudden water inflows, in im- 
proving stability, and in reducing dewa- 
tering and mining costs are goals at many 
underground operations. To identify the 
best approaches to mine water control, it 
is necessary, as a first step, to identi- 
fy the sources of water infiltration into 
the mine. Once the sources are identi- 
fied for any given mine, the potential 
solutions to reduce or control the water 
problem can then be developed. 

Water may enter mine workings via a 
number of different avenues. Water-bear- 
ing strata that are in contact with the 
coal seams can be sources of inflow. 
These strata include sandstones and lime- 
stones, which are associated with the 
coal seams, and any unconsolidated de- 
posits, such as sand and gravel, which 
may lie above the coal seams . In addi- 
tion, the coal seams themselves may con- 
tribute water to the mining environment 



and, therefore, deserve consideration as 
a source. 

The development of an underground mine 
alters the natural ground water flow 
patterns. The extent of the alteration 
is dependent on the geohydrology of the 
site and the type of mining system used. 
These aspects are briefly reviewed. 

Water may also enter shallow coal mines 
via seepage from surface water bodies 
or through general surface infiltration. 
The amount of water entering the mine 
will depend upon the nature of the strata 
above the mine and the depth to the mine. 

Earth fractures, such as faults, frac- 
ture zones, joint systems, and subsidence 
fractures, also allow water to enter un- 
derground mines. These fractures tend to 
localize inflow and destroy the confining 
effect of any relatively impermeable beds 
above the coal. They are the prevalent 
avenue by which water enters underground 
coal mines in the Appalachian coal 
region. 

Water may also enter underground mines 
through manmade pathways. Abandoned deep 
mines and active and abandoned strip 
mines can serve as sources of water accu- 
mulation and infiltration. Water from 



these sources can enter the mine workings 
directly through barrier pillars and in- 
terconnections, or these pathways may fa- 
cilitate the entry of surface runoff into 
the ground water system, which eventually 
works its way into an underground mine. 
In addition, boreholes, abandoned wells, 
shafts, and mine openings also serve as 
water collection points and direct con- 
duits to underground mines by tapping 
overlying aquifers and collecting surface 
waters. 

WATER ENTRANCE INTO MINES 

The quantity of water varies with local 
conditions during the construction or 
later development of many mines. Some 
mines are dry, while in others the weight 
of water to be removed is many times that 
of the coal raised to the surface. For 
example, at the Colver Mine in West Vir- 
ginia, the pumping load averages approxi- 
mately 31 tons of water per ton of coal 
produced, while the Sonman Mine in West 
Virginia pumps 33 tons of water per ton 
of coal produced [Coal Age (8^)]. 

Water may enter mine workings in sev- 
eral ways: 

1. From water-bearing strata that are 
in contact with coal seams; 

2. Through shallow mines from surface 
seepage; 

3. Through faults and fractures in 
coal seams and adjacent strata; 

4. Through active sections from aban- 
doned workings. 

There is considerable overlap in the 
ways that water enters the mine workings. 
For example, water may enter simultane- 
ously through water-bearing strata in 
contact with the coal seams and through 
faults and fractures from the same over- 
lying strata. Water may also enter from 
the surface via percolation or through 
faults and fractures that run through to 
the surface. Also, percolated water from 



the surface may be the source of water 
for faults and fissures, which may later 
feed the mine. Here, these pathways will 
be dealt with separately, but under 
natural conditions water may enter the 
mine workings through any means possible, 
no matter where it originates. 

In considering the problem of water 
passing into the mine workings, it is es- 
sential to take into account: 

1. The prevailing geologic and hydro- 
logic conditions , including the composi- 
tion and permeability of the associated 
coal strata and the presence of any dis- 
continuities such as faults, joints, or 
igneous intrusions. 

2. The depth of the mine workings and 
thickness of the coal seam being mined. 

3. The mining system employed and its 
effect on the prevailing geologic 
conditions. 

Underground coal mines can create a 
measurable change in water levels and 
ground water flow as a result of removal 
of water, coal, and rock from the mine. 
The removal of the water occurs by grav- 
ity drainage in the case of updip drift 
mining or by pumping in downdip drift, 
slope, or shaft mining. 

Ground water movement through aquifers 
from areas of higher piezometric pressure 
to regions of lower piezometric pressure 
has been described as follows [Wilson, 
Mathews , and Stump (43) ] : When a mine 
shaft sinks into water-bearing strata, it 
creates a region of lowered piezometric 
pressure, causing water to flow from the 
strata to the mine shaft, which in turn 
drains water from the pores and crevices 
in the strata. If pumping is started to 
remove the water, the flow into the shaft 
continues as the piezometric pressure in 
the shaft is lowered. As pumping contin- 
ues, the water level is artificially de- 
pressed and assumes the shape that a 
stretched membrane would have if punched 
downward with a stick. The water table 
has the shape of a flat, inverted cone 
with its apex at the shaft, known as the 



10 



cone of depression. However, it is not a 
true cone, since its sides, when viewed 
in cross section, are not straight lines, 
but curves that steepen toward the shaft. 

The flow of water into a mine shaft is 
heaviest when sinking begins. If sinking 
of the shaft is halted and pumping con- 
tinues at a steady rate, the flow into 
the shaft gradually decreases and after 
some time becomes virtually constant, 
equaling the rate of recharge. Accord- 
ingly, the cone of depression assumes a 
shape that is practically stable, as the 
flow of water into the shaft reaches a 
state of equilibrium with the supply of 
water entering the aquifer and percolat- 
ing through it. If shaft sinking is re- 
sumed, the process is repeated; the new 
cone is deeper and requires a higher rate 
of pumping to keep it drained. 

If a drift is extended from the bottom 
of the shaft, the cone of depression is 
no longer a symmetrical cone; what was 
formerly the point of the cone is elon- 
gated into a horizontal line, with the 
water table sloping upward from it at 
both sides and at the ends. If closely 
spaced crosscuts are driven from the 
drifts, the cone assumes the form of a 
bathtub with flat-sloping sides. If up- 
per levels are now driven from the shaft, 
they will encounter little water until 
they are out far enough to reach the 
sides of the cone. They will then begin 
to tap the water reservoir, diminishing 
the flow that enters the deepest 
workings . 

The creation of the cone of depression 
by shaft sinking provides piezometric 
highs and lows and allows for the flow of 
water into the mine when the shaft is 
lowered through water-bearing strata. 

Detecting water-bearing strata and mea- 
suring water levels and water movement 
are being increasingly recognized as a 
necessity for determining the economics 
of mining. Drilling is a means of accom- 
plishing this. Water levels and water 
movement can be delineated and studied by 
plotting the data on water level contour 
maps, water level change maps, and well 
hydrographs. 

Gallaher of the U.S. Geological Survey 
performed a study in West Virginia that 
included the drilling of 28 boreholes 



(43). In addition, 137 other private and 
public wells were investigated. The 
study determined the effect of deep min- 
ing on ground water movement. The data 
were correlated with information gathered 
from seasonal and areal distribution of 
precipitation, and the conclusions were — 

1. No two mines are expected to be 
alike in environment, hydrology, source 
of pollution, or treatment. 

2. Mining can affect speed, course, 
and quality of water moving through the 
mining area. 

3. Mining accelerates the natural flow 
and hydrogeological conditions already 
existing in the area basins. 

4. Water under pressure as a result of 
flow through strata located at elevations 
above the mine workings can enter the 
mine from all directions, including the 
floor. 

5. The chemistry of the ground water 
depends primarily on the composition 
of the minerals with which it comes in 
contact. 

6. Water samples collected at differ- 
ent depths varied widely in quality. 
Samples taken at shallow depths were less 
mineralized than those taken at great 
depths. 

COAL AND WATER-BEARING STRATA 

The strata most frequently found im- 
mediately above or below coalbeds are 
shales, clays, and sandstones. These may 
form either the roof or bottom and the 
hanging and foot walls in pitching seams. 
Conglomerates are rarely found in contact 
with the coal but are frequently part of 
the rock group associated with coalbeds. 
This is also true of limestone beds. The 
water-bearing capacity of these rocks 
will depend on their depth, since the ca- 
pacity of a rock to store and transmit 
water will decrease with depth, owing to 
the increasing pressure of the overlying 
strata. 



11 



Shales are generally the desired roof 
materials when coal is mined. This is 
because they are aquitards, having only 
minor ground water leakage through them. 
An exception to this condition is when 
clay veins or similar structures are 
present. Clay veins are slickensided 
wedges of indurated clays and silts that 
penetrate the coalbed from either above 
or below. They can be vertical or form 
an angle of about 45° with the vertical. 
Clay veins encountered in mines are usu- 
ally crooked and angular and interfinger 
with the coal. They have thicknesses 
ranging from 1 in (2.54 cm) to several 
feet (a few meters) and may be hard 
enough to damage mining equipment. Clay 
veins generally extend into the strata 
immediately overlying the coalbed, break- 
ing up the lateral continuity of the lay- 
ered roof strata, causing roof instabil- 
ity. Water can then flow into the mine 
through these zones. 

Coal itself acts as a minor aquifer 
since it possesses a fracture permeabil- 
ity, although transmissivities appear to 
vary from well to well by a factor of a 
hundred or more. Transmissivities range 
from less than 100 gpd/ft (0.14 cm 2 /s) to 
over 10,000 gpd/ft (14 cm 2 /s). An impor- 
tant aquifer characteristic of this unit 
is its widespread continuity. 

Sandstone is formed chiefly by accumu- 
lation of sands in shallow water adjacent 
to land from which stream action carries 
the material. Many of the massive sand- 
stones are extensively jointed. Even a 
rock that has little or no water-bearing 
capacity may yield water from joint 
openings . 

In Pennsylvania, the Allegheny Sand- 
stone yields from 50 to 300 gpm (3.2 to 
19 L/s), while the Pottsville Sandstone 
yields from 100 to 400 gpm (6.3 to 25 
L/s). The Pocono Formation of Pennsyl- 
vania has also yielded from 300 to 600 
gpm (19 to 38 L/s) in some places. The 
Triassic sandstones of Pennsylvania, par- 
ticularly those incorporating conglom- 
erates and f anglomerates , yield as much 
as 200 to 300 gpm (13 to 19 L/s). The 
Pottsville in West Virginia has also 
yielded over 250 gpm (16 L/s). On the 
average, sandstone aquifers yield 50 gpm 
(3.2 L/s) and are an excellent source of 



water for communities throughout the Ap- 
palachian region [Lohman ( 18) ; Doll, Mey- 
er, and Archer (11)]. 

Limestone is a hard sedimentary rock 
composed chiefly of calcium carbonate, a 
calcareous sediment that may at first 
contain a large proportion of intersti- 
tial space; however, subsequent solution 
and recrystallization accompanying com- 
paction may ultimately produce a lime- 
stone with very little original porosity. 
A seemingly impermeable rock may be rend- 
ered permeable by joints or fractures, or 
by the development of solution passages. 
Solution passages in limestone result 
from the solvent action of circulating 
ground water charged with carbon dioxide 
and usually follow preexisting joints or 
bedding planes. 

When the rock is deeply buried and the 
ground water circulation is sluggish, or 
when the rock has not been long subjected 
to solvent action, the solution passages 
may be few and small. If, however, the 
topography and geologic structure have 
favored rapid circulation, and conditions 
have been stable over long periods, the 
rock may be rendered cavernous. Some so- 
lution passages are large enough to carry 
the entire flow of a stream. The term 
"lost river" has been applied to a stream 
that disappears completely underground in 
limestone terrain. Large springs are 
frequently found in limestone areas. 

This solution of limestone proceeds 
most rapidly above the water table, where 
downward movement of the water is rela- 
tively vigorous and the supply of carbon 
dioxide is adequate. Below the water ta- 
ble, the content of dissolved carbon di- 
oxide, and consequently the solvent power 
of the water, becomes depleted. The 
largest yields are obtained from lime- 
stone that has been depressed with rela- 
tion to the water table, so that its up- 
per, cavernous areas become submerged and 
saturated. Ultimate development of a 
limestone terrain forms a karst region 
where subterranean drainage through the 
limestone creates large ground water 
reservoirs . 

In Pennsylvania, both the Cambrian and 
Ordovician limestones and dolomites yield 
abundant supplies of ground water. These 
rocks are more or less fractured, and 



12 



solution channels have been created. 
Most of the wells yield adequate supplies 
ranging from 100 to 1,000 gpm (6.3 to 
63 L/s). Boiling Springs, in Cumberland 
County, is the largest spring in Pennsyl- 
vania and yields 13,500 to 20,600 gpm 
(850 to 1,300 L/s). Bellefonte Spring, 
in Centre County, yields roughly 14,000 
gpm (880 L/s). The Devonian age Helder- 
berg Limestone also yields moderate to 
large supplies of water in Pennsylvania, 
while the springs of the Mississippian 
age Greenbrier Limestone of West Virginia 
yield more than 140 gpm (9 L/s) (18). 

As previously stated, while they remain 
intact, the shales and clays immediate- 
ly above and below the coal will not al- 
low water to infiltrate the mine work- 
ings. Occasionally though, the shale 
above the coal or the underclay is ab- 
sent. Then sandstone, and less frequent- 
ly limestone, is adjacent to the coal. 
This may result in the transmission of 
many thousands of gallons of water into 
the mine, depending on the depth of the 
mine. In the Cahaba Coalfield of Alabama 
[Johnston, Foster, and Howard (15)], con- 
glomerates and porous strata directly 
above the coal seams transmit water into 
the mines, resulting in the need to es- 
tablish a pumping system to keep the mine 
dry. In central Pennsylvania [Parizek, 
Sgambat , and Clar ( 24 ) ] , when the shale 
above the coal pinches out and sandstone 
lies on the coal, it is usually fractured 
into blocky shapes and is very difficult 
to support. 

Unconsolidated deposits of glacial, ma- 
rine, and alluvial origin can store and 
transmit huge quantities of water and can 
cause problems when in proximity to any 
coal workings. Ninety percent of all 
developed aquifers consist of these types 
of deposits [Todd (36); UOP, Inc. (37)]. 
They are widely distributed and have 
caused considerable trouble to miners in 
the past. The anthracite region of Penn- 
sylvania has been especially plagued with 
this type of problem and deserves mention 
here, even though it is not part of the 
Appalachian bituminous coal region. It 
is estimated that the northern anthracite 
field of Pennsylvania contains 10 billion 
tons (9.1 billion t) of these deposits, 



or a sufficient quantity to cover the 176 
mi 2 (450 km 2 ) of coal area to a depth of 
about 26 ft (8 m) [Bunting (_7 ) ] . These 
deposits overlying coal measures attain 
a maximum depth of more than 300 ft (91 
m) . The materials vary widely in parti- 
cle size and degree of sorting, with a 
corresponding variation in their water- 
yielding capacities. However, many are 
often saturated to the point of being 
semifluid. It is this condition of flu- 
idity that limits the mining of coal 
seams cropping in these deposits or in 
close proximity to them. 

A considerable number of inrushes have 
occurred because mine workings were too 
close to these deposits (_7, 40) . 

• In 1882, the workings at the Maltby 
Mine in Swoyersville, PA, broke into sand 
and water, which filled the mine and 
shaft to within 65 ft (20 m) of the top 
in a few hours. 

• In 1884, an inrush of sand and wa- 
ter filled the slope of the Fuller Mine 
at Swoyersville, PA, to the shaft level, 
a vertical distance of almost 100 ft 
(30 m). 

• In 1885, the inrush of a culm bank 
with sand and water completely filled the 
gangways in the vicinity in less than 1 h 
at the No. 1 Slope Mine in Nanticoke, PA. 
The accident took the lives of 26 men. 

• In 1912, an inrush of sand and water 
broke into the workings at the Superba- 
Lemont Mines in Stanton, PA, killing four 
miners. 

• In 1914, an inrush of approximately 
19,600 yd 3 (15,000 m 3 ) of semifluid sand 
and clay filled several thousand feet 
(a couple of thousand meters) of gang- 
ways and tunnels, and required months to 
clean up. The accident occurred at the 
Sugar Notch No. 9 Mine in Sugar Notch, 
PA. 

• In 1917, an inrush of sand and water 
broke into the Wilkeson Mine workings in 
Wilkeson, PA, killing six miners. 



13 



© In 1927, an inrush due to a break- 
through into 200-ft (60-m) thick gravel 
beds killed seven miners in Carbonado, 

WA. 

• In 1959, an inrush of water killed 
12 miners at the Lehigh Valley Coal Co.- 
Dillston Coal Co. in Pennsylvania when 
the workings broke into the alluvial de- 
posits of the Susquehanna River. 

The coal seams that are being mined 
currently are deep enough so that they do 
not come into contact with these types of 
deposits. However, the huge quantities 
of water contained in these deposits may 
be tapped by means other than direct con- 
tact with coal workings. These means 
will be examined in other sections of the 
report. 

WATER IN SHALLOW MINES 

Strata will tend to store and transmit 
less water with increasing depth, as the 
porosity of the strata is affected by the 
increased confining pressure resulting 
from the weight of the overburden [Ash, 
Dierks, and Miller (3); Miller and Thomp- 
son ( 2_2 ) ; Wrathers , Swanson, and Langill, 
(_44) ] • This pressure also tends to close 
up any fissures and cracks that exist. 
At depths of less than 300 ft (92 m) , it 
is comparatively easy for water to perco- 
late to a certain varying depth as a con- 
sequence of the porosity of the surface 
rocks, according to Miller and Thompson. 
The coal measures are generally very wet 
to work at these shallow depths. There 
is a marked difference between the quan- 
tity of water pumped in summer and in 
winter in the areas where water can per- 
colate rapidly into the mine workings. 

Surface Seepage 

The volume of water seeping into mine 
workings during and after any period of 
rainfall varies greatly in adjoining ba- 
sins and even in adjoining mines in the 
same field because of differences in the 
condition of the strata as affected by 
the progress of coal extraction [Ash (1), 
Ash, Dierks, and Miller (3); Ash and Link 



(4_ ) ; Ash, Link, and Romischer (_5_ ) ; Ash 
and Whaite ( 6_) ] . The ratio between run- 
off and seepage varies for each period of 
rainfall in any given area because of 
variables in (1) the rate of rainfall, 
(2) duration of storms, (3) rate of evap- 
oration (depending on temperature and 
humidity) , (4) transpiration (depending 
on the season and amount of vegetation) , 
(5) status of the water table, (6) frost 
that seals crevices in the ground, 
(7) presence of anchor ice sealing stream 
bottoms, (8) distribution of rainfall, 
(9) topography, and (10) surface soil 
condition and type. 

Surface water entering underground coal 
mines may originate either at a surface 
body or through general surface infiltra- 
tion. Any bodies of surface water may 
contain a sufficiently large volume of 
water so that significant seepage into 
underground workings could occur. Howev- 
er, the most important avenue of surface 
water seepage is that of streambed seep- 
age into underground waterways. 

Most streams that cross coal measures 
usually lose some of their water, which 
eventually enters underground mine work- 
ings. It is usually impossible, except 
in small streams, to accurately measure 
the amount of seepage that will require 
the use of corrective measures. This is 
because the loss at any particular point 
is usually very small, and the distance 
between the point where the water left 
the stream and the point where it entered 
into the mine workings may be great. 

Many different factors affect the vol- 
ume of water infiltrating mine workings. 
The following factors play a significant 
role in the inflow to mines from streams 
(3-6): (1) quantity of water flowing in 
streams, (2) velocity of the water flow- 
ing in streams, (3) nature of material 
composing the stream channel, (4) wetted 
perimeter of stream channels, (5) weather 
conditions, (6) gradient or slope of 
streams, and (7) fractures in the coal 
measures underlying the streams. 

Stream seepage will not increase sig- 
nificantly unless the volume of water 
added to the stream is enough to appreci- 
ably increase the cross section of the 
stream channel in contact with the water. 



14 



A noticeable increase in the depth of wa- 
ter flowing in the channel of a river or 
stream after a heavy rain indicates an 
increase in seepage due to the increase 
in the wetted perimeter of the stream 
channel O ) . When streams are in flood 
stage, water spreading out beyond normal 
streambanks further increases seepage. 

The anthracite region of Pennsylvania 
serves as a classic example of stream 
seepage into underground mines. Many of 
the smaller streams in the region lose 
all of their water soon after crossing 
the outcrop of the lowest anthracite bed, 
where they enter the area that overlies 
the coal measures. These streams carry 
water throughout their original length 
only during periods of heavy runoff. For 
the greater part of the year, their en- 
tire flow seeps into the mine workings. 
This flow can range from a few gallons to 
several thousand gallons per minute (3). 

A study of larger streams indicated a 
marked decrease in flow between the point 
where they intersect the coal outcrops 
and the point where they flow into the 
main stream. This was true at almost all 
periods when relatively low water levels 
permitted comparable observations. How- 
ever, at the same levels of water, such 
decrease did not occur when the bed of 
the stream was sealed by anchor ice. 
Consequently, a project is being under- 
taken in western Maryland to reline a 
streambed for a distance of approximate- 
ly 4-1/2 miles (7-1/4 km) in order to re- 
duce infiltration. Water currently in- 
filtrates through the streambed at a rate 
of roughly 15,000 gpm (990 L/s). This 
water is entering abandoned underground 
mines, causing the stream to dry up dur- 
ing the summer months. The project in- 
volves putting down a clay bottom, topped 
by a layer of sand and a layer of riprap. 
The estimated cost of the project is $3.5 
million. 

Natural surface seepage is also a prob- 
lem in permeable areas where the infil- 
tration rate is so great that some oper- 
ating companies have dug ditches and 
built flumes to divert the runoff into 
natural stream channels. In addition, 
mining operations have changed the con- 
figuration of the terrain, thereby 



affecting the original drainage patterns 
of the region. The continued increase in 
the number and size of culm banks, cinder 
dumps , and unreclaimed spoil banks has 
blocked the normal flow of water to the 
surface streams so much that water now 
collects in many low places and eventual- 
ly seeps into the ground. In addition, 
denuding woodlands destroys a control of 
runoff, and solids from breakers and 
banks pollute and choke stream channels. 
The dry beds of thousands of small former 
watercourses are evidence of the general 
disturbance of the surface (3-_6 ) . 

Surface Water Inrush 

In considering the problems of water 
passing from a surface source into mine 
workings, the proximity of mining to a 
given body of water is a vital factor in 
the risk of inundation. Another impor- 
tant factor is that the height of a roof 
fall can be in part related to the height 
of workings and in part to the nature of 
the solid strata between the workings and 
the streambed. 

Studies in the anthracite region of 
Pennsylvania are presented here to pro- 
vide a clearer picture of the quantity of 
water capable of entering underground 
coal mines via stream and surface seep- 
age. One study involved the Lackawanna 
Basin and the Wyoming Basin of the North- 
ern Field, the Western Middle Field, and 
the Southern Field (3-6.) • 

The Lackawanna River and its tribu- 
taries drain a troughlike area of 347 
mi 2 (900 km 2 ). The synclinal axis of 
this trough lies within the coal mea- 
sures. For 1948, the U.S. Weather Bureau 
recorded 44.9 in (114 cm) of rainfall, 
indicating that there were 135 billion 
gal (510 billion L) of runoff from the 
Lackawanna River drainage area. This is 
approximately three times the volume of 
water pumped for this area in 1948. Be- 
cause of the pervious condition of the 
strata overlying the mine workings, ap- 
proximately one-third of the total runoff 
in the Lackawanna River area becomes mine 
water. Approximately 22 pet of this wa- 
ter arrives underground as a result of 
direct surface seepage. In addition, an 



15 



equal volume seeps into the mine workings 
through the pervious beds of 52 streams. 
The remaining 56 pet of the pumped water 
seeps underground through the bed of the 
Lackawanna River. 

Similarly, the Susquehanna River and 
its tributaries drain an area of 169 mi 2 
(437 km 2 ) overlying the Wyoming Basin. 
Even though this is slightly less than 
half the size of the Lackawanna River 
drainage area, the total volume of water 
pumped to the surface is 21 pet more than 
in the Lackawanna Basin. The average 
volume of water pumped per year is 112 
billion gal (425 billion L) , which corre- 
sponds to more than 214,300 gpm (13,500 
L/s) pumped against an average hydro- 
static head of 394 ft (120 m) . It is 
difficult to achieve good runoff because 
of the relatively flat terrain created 
by the wide floodplain in the Wyoming 
Valley. Consequently, much of the sur- 
face water seeps directly into the 
ground, eventually ending up in the mine 
workings . 

Approximately 30 pet of the seepage wa- 
ter is direct surface seepage, while 
another 21 pet seeps through the pervious 
beds of 59 streams. The remaining 49 pet 
seeps through the bed of the Susquehanna 
River. 

In contrast to these two basins, the 
Western Middle Field and the Southern 
Field do not have major rivers overlying 
them. Therefore, there is a higher per- 
centage of mine water from surface seep- 
age. In 1951, 36 billion gal (136 bil- 
lion L) were pumped to the surface from 
the Western Middle Field, while 17 bil- 
lion gal (64 billion L) were pumped from 
the Southern Field. This corresponds to 
roughly 67 pet and 34 pet of the total 
runoff into the respective drainage 
areas. The general surface seepage in 
the coal areas is 90 and 92 pet, respec- 
tively. The remaining 10 and 8 pet are 
seepage from the streambeds. 

In the bituminous region, surface res- 
toration and stream reconstruction have 
also been underway to check water inflow 
due to seepage. A project involving the 
construction of a new channel on Little 
Sandy Run in north central Pennsylvania 
was undertaken in 1974 [Klingensmith , 



Miorin, and Saliunas (17) ] . The channel 
was to be constructed approximately 1,000 
ft (305 m) over underlying mine workings. 
A significant loss of streamflow had been 
noted here during earlier watershed in- 
vestigations. The area was cleared and 
grubbed; the new channel was excavated; 
the existing channel was filled; a layer 
of sand and bentonite was placed as an 
impermeable membrane in the new channel; 
riprap protection was provided for the 
impermeable membrane; two underdrains 
were laid to convey acid water from new 
mine pool overflows (possibly caused by 
Hurricane Agnes in June 1972) into the 
new channel; and the affected area was 
graded, limed, fertilized, and seeded. 
This work was completed in September 
1974, at a total construction cost of 
$96,545.97. This channel also success- 
fully carried the runoff from Hurricane 
Eloise in September 1975.' No maintenance 
has been necessary since construction was 
completed. An estimated average infil- 
tration of 400,000 gpd (1.52 million L/d) 
of water was prevented from entering the 
underlying mine workings. 

Another project involved the recon- 
struction of the streambed of a headwa- 
ter's branch of Morris Run (17) . The re- 
constructed streambed was first lined 
with a layer of locally available clay, 
which was then covered by a protective 
filler blanket and quarry stones. The 
entire area was then limed, fertilized, 
and seeded. The total construction cost 
of this project, which was completed in 
October 1975, was $453,925.20. This 
project, together with the reclamation of 
two adjacent strip mines, has prevented 
an estimated average daily infiltration 
of 1.25 million gpd (4.73 million L/d) of 
water into underlying mine workings. 

These data indicate that huge quanti- 
ties of water can enter mine workings as 
a result of seepage , and because of the 
seriousness of this problem, preventative 
measures must be taken. 

WATER ENTRANCE THROUGH FRACTURES 

Earth fractures, such as faults, frac- 
ture zones, joint systems in rocks, and 
fractures caused by surface subsidence, 



16 



allow water to enter underground mines 
in various quantities. They are a major 
avenue of water entrance into underground 
mines, because coal measures are usually 
overlain by impervious strata consisting 
of shales. No water will enter the mine 
from the surface or from any aquifer 
above the coal seam if these strata re- 
main intact. 

Fracture flow, which tends to local- 
ize inflows, is prevalent within the 
eastern margins of the bituminous coal 
region. These zones of fracture concen- 
trations show up on the surface as frac- 
ture traces. These fracture traces have 
been used to locate highly productive 
water wells with aerial photography, and 
more recently, with remote sensing. 
Here, subtle lines are present on the 
Earth's surface; indicators include more 
lavish vegetation due to ground water in 
decomposed rocks, surface sags and de- 
pressions, and stream valley alignments. 
There is often an abundant supply of wa- 
ter where two or more of these fracture 
traces intersect. Wells drilled at these 
intersections have yielded up to 3,000 
times more water than wells drilled at 
random. 

Joints 



A joint is a fracture in a rock in 
which there is no observable relative 
movement between the sides. A series of 
parallel joints is called a joint set, 
while two or more sets intersecting pro- 
duce a joint system. 

Joints are important because they lo- 
cally control drainage patterns and be- 
cause they provide a passage through 
which water may penetrate deeply into a 
rock mass, thus allowing weathering to 
take place. This is especially evident 
in limestone, where the end result of 
this weathering is karst scenery. In ad- 
dition, joints increase the porosity and 
permeability of a rock mass, thereby cre- 
ating aquifers in previously impervious 
strata. If they are developed enough, 
the joints can also tap overlying aqui- 
fers and water sources, and provide flow 
paths to the mine workings. 

The intergranular permeability of shale 
is relatively low because the rock is 



fine grained and lithified. Shales have 
a high porosity relative to most sand- 
stones, but the interstitial spaces are 
so minute that the water movement is re- 
stricted. For this reason, shales usual- 
ly provide an excellent means for keeping 
water out of underground mines . Howev- 
er, where shales are jointed, they have 
provided significant water supplies to 
users. In many rocks, shales and joints 
are the principal means by which the wa- 
ter is stored and transmitted. 

Wells penetrating strata whose water 
capacity is determined by joints yield 
up to 200 gpm (13 L/s), with most wells 
yielding 50 gpm (3 L/s). Pre-Cambrian 
rocks of southeast Pennsylvania, consist- 
ing of schists, slates, and crystalline 
rocks, yield up to 100 gpm (6 L/s), while 
the rocks in the lower Cambrian sand- 
stones, quartzites, and conglomerates 
yield up to 200 gpm (13 L/s) (18). 

Joints tend to close and heal with 
depth, resulting in a decreasing yield 
of ground water. Closed joints are some- 
times called latent, blind, or incipient. 
The majority of open joints are close to 
the ground surface, and significant flows 
are encountered, usually in the first 100 
ft (30 m) of excavation (44) . With in- 
creasing depth, the increased confining 
pressure caused by the overburden weight 
tends to limit the space created by 
jointing. At depths greater than 300 ft 
(90 m) , the water storage capacity of 
joints becomes less significant. Howev- 
er, the presence of higher differential 
heads in deep mines tends to negate the 
advantage of lower permeabilities created 
by this healing, resulting in the inflow 
of stored water into the mines. 

Faults and Fracture Zo nes 

Faults can cause water problems in un- 
derground coal mines by (1) acting as a 
water reservoir, releasing water when 
tapped by the mine workings, and (2) act- 
ing as a conduit, hydraulically connect- 
ing a water source, such as an aquifer 
or surface water body, to the mine work- 
ings. Faults and fracture zones can also 
cause very bad roof conditions, espe- 
cially if a significant amount of water 
is present. As a rule, jointing and 






17 



faulting tend to coincide in folded re- 
gions. No real distinction is made be- 
tween faults and joints since both act as 
conduits, transmitting water from other 
sources to the mine workings. 

The most noteworthy example of how 
faults can be a cause of inundations is 
the flooding of the Higashisome Colliery 
in Japan in 1915. (Although collieries 
in Japan are outside the scope of this 
report, they serve as excellent examples 
of how costly, in both production and 
safety, a fault zone can be.) On April 
12, 1915, an estimated 10.5 million ft 3 
(0.3 million m 3 ) of water flooded the en- 
tire mine in 2 h , killing 237 workers. 
The source of the flooding was a fault 
that acted as a hydraulic connection be- 
tween a seabed above the workings and the 
workings themselves. The fault extended 
155 ft (47 m) through a sandstone bed, 
and another 83 ft (25 m) through an allu- 
vial deposit of clay and sand (40) . 

Japanese collieries have been known 
to be susceptible to flooding through 
faults. In 1934, 54 lives were lost when 
the Matsushima Mine was flooded. Here 
the fault penetrated over 200 ft (61 m) 
of cover to a surface seabed. In 1942, 
183 miners were killed when the Chosei 
Mine was flooded by seawater penetrating 
119 ft (36 m) through a fault (40). 

In the United States, fracture-domi- 
nated flows have not been as severe. In 
some cases , especially where the fault 
zone is serving as a storage reservoir 
and the recharge to the fault zone is 
limited, water inflow is virtually negli- 
gible. Republic Steel's North River No. 
1 Mine in Berry, AL, exemplifies this. 
Here, the major source of water is from 
water-bearing fractures. The workings 
are dry, except when occasional water- 
bearing fracture zones are penetrated by 
mine openings. The initial penetration 
of water-bearing openings usually re- 
leases a large inflow averaging 200 to 
300 gpm (12.6 to 18.9 L/s). This would 
be a problem should this inflow remain 
constant. However, after a period of 
time, the flows decrease to a trickle, 
indicating that the water storage system 
is very restricted both vertically and 
laterally [Shotts, Sterett, and Simpson 
(31)]. 



The Lancashire No. 20 Mine near Car- 
rollton, PA, illustrates another feature 
of fracture-dominated flows (38) . Here, 
baseline monitoring of water quantities 
established that the flows responded rap- 
idly to wet and dry conditions in spite 
of a depth of over 500 ft (152 m) . This 
rapid response indicated that the frac- 
ture zones had a hydraulic connection to 
the surface. It was even possible to 
recognize recharge from individual rain- 
storms. Geologic investigations indi- 
cated that the fracture zones consisted 
of steeply dipping fractures that inter- 
sected the surface, permitting rapid 
recharge from precipitation and from 
streams or ponds on the surface. It was 
noted that secondary aquifers also fed 
the fracture zones. 

Mine Subsidence Fractures 



Mine roof fracturing and the resulting 
surface subsidence following the removal 
of mine roof supports such as pillars and 
blocks is one primary cause of water en- 
trance into deep mines. Here, water de- 
scends on fractures resulting from the 
subsidence of mined-out ground. Such 
fissures form direct conduits that carry 
water. It has been found that as pil- 
lars are removed, the cost of pumping in- 
creases greatly. In some of the Pratt 
Mines (Alabama), where pillars were 
robbed as the entries were driven to the 
boundary, from 10 to 15 tons of water 
were pumped for each ton of coal produced 
U5). 

Whittaker, Singh, and Neate (42) have 
attempted to quantify the effects of 
subsidence on the increased permeability 
of these zones in England. Although this 
work was done in England and not in the 
Appalachian coal region of the United 
States , it is the only current investi- 
gation that quantifies the effects of 
subsidence. One of the studies was per- 
formed in the East Midlands Coalfields, 
involving the deep soft seam. The re- 
treating longwall mining method was em- 
ployed in the study. The mine was 1,970 
ft (600 m) deep and had a longwall face 
width of 690 ft (210 m) , and the seam was 
31 in (80 cm) thick. The results showed 
that the closer the stratum was to the 



18 



coal seam, the more the permeability was 
increased by caving. 

A second site investigated by Whit- 
taker, Singh, and Neate (42) was the 
Yorkshire Coalfield. Here, the shallow 
Wood Seam at Wentworth was being rained 
by the retreating longwall method. The 
depth of the seam was rather shallow at 
175 ft (53 m) . Results showed that a 
discernible change in the waterflow was 
taking place at 164 to 197 ft (50 to 60 
m) ahead of the face line. This flow in- 
creased in marked steps, indicating the 
opening and closing of near-surface 
cracks and fissures. The flow curve set- 
tled to a constant value of about 98 to 
131 ft (30 to 40 m) behind the face line. 
The onset of permeability change occurred 
significantly ahead of the face line with 
the upper test strata in comparison with 
the lower test strata. 

A third site investigated ( 42 ) was the 
Lyneraouth Mine. Here, the seam under 
consideration was the Brass Hill Seam. A 
retreating longwall method was being used 
on a 3.3-ft (1-m) seam. The face length 
was 600 ft (183 m) . Static head measure- 
ments were taken at six different depths 
in two boreholes. The lowest test sec- 
tion showed the largest change in static 
head, with the higher sections displaying 
progressively less change. However, per- 
meability changes occurred first in the 
higher test section. 

All test results show a marked increase 
in the permeability of the strata as a 
result of subsidence. Marked increases 
in flow rates were also observed. It is 
important to compare the quantity of wa- 
ter flowing when a possible aquifer is 
tapped by the fracturing, with that flow- 
ing when only the immediate roof , con- 
sisting of relatively impervious strata, 
is tapped. 

Another example of water inflow in un- 
derground deep mines that was due to sub- 
sidence occurred at the Jones and Laugh- 
lin Steel Corp.'s Shannopin's Section No. 
1 Mine in Greene County, PA [Doyle, Chen, 
Malone, and Rapp (12)] . The Pittsburgh 
Coal Seam was being mined. It has a min- 
able thickness of about 6.6 ft (2 m) . 
Section 1 underlies Dooley Run drainage 
basin, which during the investigation 
had no flow. The method of mining was 



retreat room-and-pillar , which resulted 
in surface subsidence and fracturing of 
the overlying rock strata. The overbur- 
den thickness of 350 ft (107 m) was not 
sufficient to prevent the total loss of 
streamflow. The river flow was estimated 
at 1 ft 3 /s (28 L/s), which corresponds to 
a loss of 650,000 gpd. The researchers 
concluded that essentially all precipita- 
tion within the drainage basin (less the 
loss through evapotranspiration) is per- 
colating into the mine through subsidence 
fractures and fissures. This is an exam- 
ple of mine subsidence capturing most of 
the precipitation falling in the drainage 
basin. 

ABANDONED DEEP MINES 

Flooding of abandoned mines is a major 
factor affecting the future of the coal 
industry. The proximity of these flooded 
mines to active workings results in the 
infiltration of water either through bar- 
rier pillars, which separate the aban- 
doned workings from the active workings, 
or through interconnections [Ash, Cassap, 
Eaton, Hughs, Romischer, and Westfield 
(2); Peters, (26)]. Therefore, the aban- 
donment of a mine and suspension of pump- 
ing in that mine tends to increase pump- 
ing costs for adjacent mines. Adjoining 
mines must prepare to handle more water 
seeping through barrier pillars or main- 
tain the water in the abandoned mine at 
such an altitude that the barrier pillar 
will not fail or allow excessive seepage. 
Thus, the operating mines gradually as- 
sume the pumping loads of all abandoned 
mines in their basin. This is impossible 
in some mines so mine pumps have been in- 
stalled in abandoned mines to prevent the 
flooding of active mines. 

Barrier Pillars 

Coal mines are usually separated by 
barrier pillars, which are formed by 
leaving part of a coal seam unmined along 
the lines of adjoining mining properties, 
or between mines or parts of mines. The 
principal function of barrier pillars 
is to act as a dam to confine accumu- 
lating mine water and prevent it from 
seeping, flowing, or breaking into an 



19 



adjacent mine and causing loss of life 
and property [Ash, Cassap, Eaton, Hughs, 
Romischer, and Westfield (2 ) ; Dierks, 
Eaton, Whaite, and Moyer (10) ] . 

A barrier pillar should be designed to 
hold water in abandoned mines under high 
head, since the pressure may be suffi- 
cient to force water through the strata 
either above or below the otherwise ade- 
quate barrier pillar. The size of these 
barrier pillars is based on (1) the ex- 
tent of waterlogged workings and accumu- 
lation of water, (2) physical-mechanical 
properties of coal, (3) presence of geo- 
logical disturbances, and (4) head of wa- 
ter against the proposed drivages [Gulati 
and Singh (14) ] . 

The path of seepage in the vicinity of 
a coal barrier will depend on the flow 
gradient and position with relation to 
major circulation. In downward circulat- 
ing zones , seepage tends to occur along 
and under the coal, with a smaller amount 
over the coal. In upward circulating 
zones, seepage tends to occur along and 
over the coal, with perhaps a smaller 
amount under the coal. The underclay 
significantly prevents seepage below the 
coal (22). 

Investigations have revealed that the 
extent of damage to many barrier pillars 
during subsidence cannot be anticipated 
since many are too small, or are partly 
removed, punctured, or encroached upon 
(_32_) . The extent of bridging of roof 
rock above a mined coal will affect the 
ability of a barrier to restrict seepage. 
Undisturbed permeability in roof rock 
will be limited to a wedge of unfrac- 
tured rock above the barrier. A highly 
permeable bed close to the level of the 
coal will also decrease the effectiveness 
of seepage restriction by a barrier, es- 
pecially in the presence of subsidence 
fractures. In addition, barrier pillars 
often are punctured by passageways in 
which masonry or concrete dams are con- 
structed to resist hydrostatic pressure. 
However, a masonry dam can fail even be- 
fore the barrier pillar itself collapses 
if the barrier pillar is unstable. 

The abandoned flooded portion of the 
Republic Steel Corp.'s Clyde Mine, in 
Washington County, PA, is the largest 
source of water infiltration to Bethlehem 



Steel Corp.'s Marianna No. 58 Mine to the 
west. The Clyde Mine is higher up, and 
the impounded water behind the barrier 
pillar that separates the two mines seeps 
through fractures. Percolation reduction 
would require at least 9,600 ft (3,000 m) 
of grout curtain to seal the fractures 

(j_2). 

At Jones and Laughlin Steel Corp.'s 
Shannopin Mine Complex in Greene City, 
PA, sections 1 and 2 experience water in- 
filtration of about 750,000 gpd (30 L/s) 
from the worked-out sections of the Maid- 
en Mine. The water infiltrates through 
barrier pillars (12). 

Present-day problems would be much sim- 
pler if the need for and value of barrier 
pillars had been understood 75 yr ago, 
when mining at depth was getting under- 
way. Unfortunately, particularly in the 
anthracite coal region of Pennsylvania, 
lands were not generally controlled in 
large blocks by one company or individ- 
ual; because of the irregular shape of 
holdings, the quantity of coal that would 
have had to be left for adequate barrier 
pillars was too great to be considered. 
In the past, barrier pillars were not es- 
tablished soon enough. Excavations were 
made too close to property lines before 
there was any attempt to establish a 
barrier pillar. 

Interconnections 



Abandoned deep coal mines are usually 
not completely separated from the active 
workings by barrier pillars. Great min- 
ing activity with the resultant abandoned 
and waterlogged workings results in the 
connection of both active and abandoned 
workings by shafts, boreholes, cross- 
measure drifts, and in-seam roads. These 
interconnections permit water from inac- 
tive mines to enter the active workings. 
Unreliable old mine maps compound the 
problem, because the extent of the water- 
logged workings is not always known. 

Large quantities of surface water are 
often collected by nonregraded surface 
mines. These mines usually consist of 
open pits with no surface exit point for 
this water. Water collecting in these 
pits can then infiltrate into any near- 
by underground mines. Many active and 



20 



abandoned underground mines also out- 
crop into areas that have been contour- 
stripped. This provides a direct hydrau- 
lic connection into an underground mine. 
In addition, water collected by a surface 
mine on the updip side of an underground 
working can enter the working through a 
permeable coal seam, either directly or 
by entering the ground water system. 

Recontouring and revegetation of the 
strip mines located above an underground 
mine should control and reduce ground wa- 
ter infiltration. Improved contouring 
for surface drainage would favor surface 
runoff. Vegetation will hold water and 
increase evapotranspiration. The addi- 
tion of limestone to the cover, in con- 
junction with revegetation, would improve 
the quality of water seeping into the wa- 
ter table. Draining the strip pits would 
accompany recontouring and would lessen 
vertical leakage. The pits could be 
drained with ditches without recontouring 
or by installing pumps and piping. 

At the Beech Creek Mine in northern 
Pennsylvania, the restoration of an aban- 
doned strip mine reduced the amount of 
water flowing into the underground work- 
ings to approximately 36,000 gpd (2 L/s). 
The work included backfilling and regrad- 
ing, providing ditches and flumes to con- 
vey surface water across the restored 
strip mine, liming, fertilizing, and 
seeding the area (17) . 

Another site where waters were entering 
underground mines through the surface 
mines was near Williamsport , PA, at the 
Tioga River (17) . Here, an inactive 16- 
acre (6.5-hectare) strip mine partially 
full of water was restored, a streambed 
running across the mine was recon- 
structed, and the entire area was limed 
and fertilized. Also, an 80-acre (32- 
hectare) portion of an inactive strip 
mine was restored and graded to blend 
into an adjacent, previously restored 
strip-mined area. This has prevented an 
estimated daily infiltration of 1.23 mil- 
lion gpd (50 L/s) of water into underly- 
ing deep mine workings. 

Active strip mines have also been known 
to create water problems for underground 
coal mines. In Great Britain, the Aber- 
pergum Colliery had its main returns 
blocked when water from the Maesgwyn Cap 



Opencast Site entered them in 1963 [Dav- 
ies and Baird (9_) ] . On December 30, 
1974, the pumps at Tower No. 4 Shaft of 
Tower-Ferhilt Mine were overwhelmed by 
water after the pillar that had separated 
old workings in the 9-ft (3-m) seam at 
Tower from the disused workings of Rhigos 
Mine had been penetrated by the Dunraven 
Opencast Coal Site. The result was over- 
flowing sumps and flooded roadways, and 
the obstruction of one roadway serving 
as a return from a longwall face. When 
opencast operations are allowed to en- 
croach on old workings connected with 
working mines , there is a risk of inun- 
dation. The likelihood of flooding in- 
creases during periods of high rainfall. 

Boreholes, Wells, and Shafts 

Boreholes and abandoned wells act as 
water collection points and conduits to 
underground mines. They are usually ver- 
tical, or near vertical, and tap overly- 
ing aquifers and surface waters. They 
are usually drained when the holes are 
penetrated during mining. 

Shafts and mine openings are very simi- 
lar to boreholes and abandoned wells 
since they act as water collection points 
and conduits to underground mines by tap- 
ping overlying aquifers and collecting 
surface waters. The difference is that 
they are usually an integral part of 
the mining operation, and therefore can- 
not be sealed. An example of this is 
the Shidler Air Shaft located in an 
abandoned section of Marianna No. 58 Mine 
in Washington City, PA. The air shaft 
provides some ventilation of active 
operations, and sealing the shaft would 
affect mine ventilation (32). 

It is evident that there are a consid- 
erable number of avenues by which water 
may enter underground coal mines. Most 
of these avenues are interrelated in that 
any one source could feed any number of 
other sources; for example, seepage could 
feed faults, aquifers, abandoned mines, 
or the mine itself. The danger of a sud- 
den influx of water from an overlying 
flooded mine, as strata are disturbed by 
pillar extraction in the lower bed, can- 
not be overemphasized. 



21 



Knowledge of the various sources of wa- 
ter inflow will assist the mining engi- 
neer in identifying sources of inflow to 
a specific mine, in the planning and de- 
sign stages. Early identification of the 
sources of water inflow together with the 



information on water control practices 
provided in the following section will 
enable the mining engineer to evaluate 
and select the most effective method(s) 
of water control. 



WATER CONTROL PRACTICES 



This section discusses practices that 
have been used, or proposed for use, to 
control the inflow of surface and ground 
water into active underground coal mines. 
This compilation was obtained by review- 
ing the available literature and select- 
ing those practices that are designed to 
be preventative in nature, rather than 
prescriptive. Thus, the common objective 
of all of the practices described is to 
prevent or reduce the inflow of water in- 
to active mines for the implicit purpose 
of reducing the costs of coal production 
by improving one or all of the three cat- 
egories previously discussed: (1) health 
and safety, (2) production, and (3) the 
environment. 

Ten water control practices are de- 
scribed. Although each practice is de- 
scribed separately, they can be grouped 
according to whether they are designed to 
control surface or ground water inflow. 
Figure 2 is a matrix listing the 10 con- 
trol practices and indicating which of 
the sources of water inflow, previously 
discussed, can be controlled by the use 
of these practices. The first five prac- 
tices described in this section are suit- 
able primarily for controlling surface 
water inflow, while the last five prac- 
tices described are suitable primarily 
for the control of ground water inflows. 

The water control practices presented 
are not universally applicable, and the 
choice of a particular technique to use 
for a given situation will ultimately de- 
pend on the cost effectiveness of the 
technique. The cost effectiveness of the 
technique will depend on the hydrogeo- 
logical conditions in the area and the 
benefits derived from the use of the 
practice with respect to health and safe- 
ty, production, and the environment. 
Unfortunately, the literature evaluation 
revealed that the technical feasibility 



and cost effectiveness of many of these 
practices have yet to be determined. 
Many of these practices were selected be- 
cause they represented the best, and in 
some instances the only, available con- 
trol technology. However, provisions 
were seldom incorporated to monitor the 
short- or long-term performance of these 
controls. 

For example, an interim report prepared 
by Schmidt and Ahnell (28) for the Bureau 
describes the tasks necessary for the ap- 
plication of a mine dewatering strategy 
and the implementation of a dewatering 
scheme at a mine in Preston County, WV. 
Results of the mine dewatering efforts 
were inconclusive, partly because of 
problems encountered in attempting flow 
measurements inside the mine. The depth 



s 




Surfoce woter controls 


Ground water controls 


^ x Water controls 

N 


o 
o 

3 C 

en O 

*o S o> 
o*5.| 


"o 

4) o 

3 2 


c 

T3 
P O* 

O..E 

"£ TD 
3 C 
CO O 


c 

o 


o rz 

4) T3 

$> E 


Reduce 
permeability of 
overlying strata 


E 

is 
11 




\ 

Water sources \ 
\ 
\ 
\ 


c 
'5 

o 3 

c C 

3 3 
O O 


O 

CD 


8 

a 

if 

■"=> o 

3 A) 

in Si 




Cool ond contact- 
ing water-bearing 
strata 


Strata associated 
with coolbeds 












• 








• 


Other strata serving 
as a woter source 












• 


• 




• 




Surfoce water body 
seepage 






















Surfoce woter 
entrance 


General surfoce 
seepage 


• 


• 


• 


• 








• 








Surface water inrush 




• 


• 


• 


• 














Joint system in rocks 












• 








• 


Water entronce 
through fractures 


Foults and fracture 
zones 










• 


• 








• 




Mine subsidence 
fractures 






• 


• 


• 


• 




• 




• 




Abandoned under- 
ground mines (barrier 
pillars, interconnections) 












• 






• 




Constructed 
pathways 


Abandoned ond active 
surfoce mines 
















• 








Borings, boreholes, 
gos ond oil wells 


• 


• 


• 








• 










Shafts ond 

mine openings 


• 


• 


• 






• 






• 





• Indicates that water control techniques can be used to control the water source 

FIGURE 2. - Matrix of mine water controls 
versus mine water sources. 



22 



of cover at this time ranged from 100 
to 300 ft (31 to 92 m) , considerably 
shallower than the average depth of min- 
ing in the Appalachian region, which is 
approximately 600 ft (183 m) . A cost 
analysis of this dewatering was not 
available. 

SITING SURFACE FACILITIES AND OPENINGS 

A considerable amount of water can be 
prevented from entering underground mine 
workings simply by proper siting of sur- 
face facilities and mine openings. Im- 
portant considerations in siting sur- 
face facilities and openings are access, 
surface rights , power and water avail- 
ability, government and municipal re- 
strictions, material availability, sur- 
face space, topography, wind direction, 
floods, slides, and costs. All of these 
considerations may have an effect on 
how much water may enter the mine. Bore- 
holes, shafts, and other mine openings 
should not be located in floodplains, 
naturally depressed areas, or other low- 
lying areas that retain surface runoff, 
since water accumulating in these areas 
will enter the mine through these open- 
ings. In addition, surface facilities 
located in these areas will tend to pud- 
dle water, enabling it to infiltrate into 
the mine via surface water-body seepage 
and general surface seepage. 

SURFACE RUNOFF DIVERSION 

The amount of water with potential to 
enter an underground mine can be con- 
trolled by reducing the amount of surface 
runoff that enters the area overlying 
a mine. Surface runoff can infiltrate 
the soil and eventually enter the mine 
through surface water-body seepage and 
general surface seepage. Ponding of sur- 
face runoff may also cause water to en- 
ter an underground mine via surface wa- 
ter inrush. In addition, surface runoff 
can collect and enter abandoned and ac- 
tive surface mines, borings, boreholes, 
gas and oil wells, and shafts and mine 
openings , thereby finding direct access 
into underground mines in many instances. 
Surface runoff diversion is the process 



of intercepting and channeling the sur- 
face runoff to natural watercourses be- 
fore it reaches these potential infil- 
tration sources. 

Methods for diverting surface runoff 
include ditches, trench drains, flumes, 
pipes, and dikes. Diversion ditches are 
frequently used to divert surface water 
around the mine area. Flumes and pipes 
are used to convey water across surface 
cracks and subsidence areas. Dikes can 
be used for the same purpose as ditches; 
however, they are often used together, 
with the excavated material from the 
ditch used to form the downslope dike. 

Advantages of surface runoff diversion 
methods include low maintenance require- 
ments, relatively low cost, a potential 
for a high degree of effectiveness, and a 
long service life. 

The disadvantages include the need for 
surface restoration once mining is com- 
plete and the need for obtaining 
access to the surface land required for 
construction of the diversion facilities. 
Underground mining companies may not own 
all of the surface land needed for diver- 
sion facilities and, consequently, may 
not have ready access to modify the sur- 
face drainage patterns. An additional 
disadvantage may be that the diversion of 
surface runoff into streams, especially 
during maximum flow conditions, can ag- 
gravate flooding and erosion problems 
downstream. 

In most cases, the cost of surface wa- 
ter diversion will be less than the costs 
involved in treating an equal volume 
of mine water to meet acceptable stan- 
dards. Surface water diversion costs 
will vary depending on the following 
factors: topography, availability of 
equipment, type and condition of soil, 
size of area, and quantity of water 
expected. 

SURFACE REGRADING 

The amount of water available to infil- 
trate the soil and, eventually, the 
underground mine can be decreased by in- 
creasing surface runoff over the overly- 
ing surface area. Surface runoff can be 
increased by regrading selected areas to 



23 



provide a better drainage configuration, 
thereby limiting the amount of surface 
water-body seepage, general surface seep- 
age, and surface water inrush that can 
occur. Areas suitable for regrading are 
those that retard the flow of surface 
runoff, thereby providing the opportu- 
nity for water to enter the soil strata. 
These areas include natural depressions, 
depressions caused by subsidence, or non- 
regraded surface mines. Nonregraded sur- 
face mines are a common source of under- 
ground mine water in the Eastern United 
States where coal outcrops are contour- 
stripped. Depressions occurring around 
borings, boreholes, gas and oil wells, 
and shafts and mine openings are particu- 
larly important in that a considerable 
amount of water can freely enter an un- 
derground mine through these avenues. 

The effectiveness of a particular ap- 
plication of surface regrading will 
depend on the site hydrology. On-site 
evaluations are necessary to determine 
the amount of infiltration caused by cor- 
rectable situations. This amount can be 
estimated by using flow measurements and 
by comparing the infiltration capacity at 
similar adjacent undisturbed areas. 

The amount of water that can be pre- 
vented from infiltrating the soil as a 
result of regrading depends on the fol- 
lowing factors: the size of the drainage 
area that is tributary to the depressed 
area, annual precipitation rates, and the 
change in runoff coefficients caused by 
the filling and grading activities. 

Strip mines can intercept underground 
mine workings along the highwall. If in- 
terception takes place on the updip side 
of an underground mine, a significant 
amount of surface runoff can be conveyed 
to the underground mine workings. The 
regrading method should be designed to 
divert surface runoff from the highwall. 
In addition to regrading, ditches and 
flumes can be constructed to aid in in- 
creasing surface runoff. Impervious 
materials or spoil material can be com- 
pacted against highwalls before backfill- 
ing to prevent water from flowing into 
adjacent mines. 

The advantages of surface regrading are 
similar to those for surface runoff 



diversion: low maintenance requirements, 
relatively low cost, a potential for a 
high degree of effectiveness, and a long 
service life. An additional advantage is 
the restoration of abandoned areas. 

The disadvantages include the need for 
obtaining access to the use of the sur- 
face land and the possibility that the 
increase in surface runoff into streams, 
especially during periods of maximum 
flow, could aggravate flooding and ero- 
sion problems downstream. An additional 
disadvantage for regrading and restoring 
surface mines involves assessing the re- 
sponsibility for performing the work. 
The mining company involved with surface 
mining may not be the same company in- 
volved with underground mining. 

The costs of surface regrading and re- 
storing depend on factors such as the 
length and height of the highwall, the 
number of cuts made, the size of the af- 
fected area, the degree of regrading nec- 
essary, the method of revegetation, and 
whether surface mining reclamation activ- 
ities are included in the mining opera- 
tion or take place sometime after mining 
activities have stopped. The costs for 
surface regrading and restoration may in- 
clude clearing and grubbing, backfilling, 
grading, revegetation, establishing mine 
access, diversion ditches, flumes, and 
seals. 

A project to control water infiltration 
by regrading a surface mine was under- 
taken in the Roaring Creek-Grassy Run wa- 
tersheds near Elkins, WV [Scott and Hays 
(29) ] . The contour method of regrading 
was used when the highwall was fractured 
and unstable, and the pasture and swal- 
lowtail regrading methods were used when 
the highwall was stable. Also included 
in this project was sealing of an opening 
in the highwall to prevent water from in- 
filtrating through the opening and into 
an adjacent underground mine. Represen- 
tative costs for this reclamation are 
shown in table 2. 

The actual effectiveness of this re- 
grading project was difficult to deter- 
mine because of cost overruns, and in- 
complete reclamation and sealing of a 
large underground mine. A preliminary 
evaluation, however, revealed that flow 



24 



in streams adjacent to the regraded area 
was increasing, which indicates an in- 
crease in surface runoff and a decrease 
in the amount of water entering the soil 
strata. 

SOIL SEALING 

Another method of increasing surface 
runoff and, subsequently, reducing the 
amount of water infiltration is to reduce 
the permeability of the surface soil. 
The permeability can be reduced by seal- 
ing the soil with an impermeable mate- 
rial, which will limit the amount of 
surface water-body seepage and general 
surface seepage. Soil sealing may also 
be effective in cases of potential inrush 
occurring from surface runoff. Mine sub- 
sidence fractures extending to the sur- 
face may also be partially sealed at the 
surface. Soil sealing can also be used 
on soils in active and abandoned surface 
mines to limit the seepage of water pond- 
ing in these mines into underground 
mines. Materials that have been investi- 
gated for soil-sealing purposes include 
clay, asphalt, concrete, rubber, and 
plastic. 

Soil sealing is often used in conjunc- 
tion with other water infiltration con- 
trol methods. For example, areas that 
have subsided because of mining activi- 
ties are often filled and graded to pro- 
vide better surface drainage patterns. 
In addition to filling and grading, im- 
permeable materials can be placed in the 
area, compacted, and graded to increase 
the rate of surface runoff. Another 



example is the placement and compaction 
of impermeable materials against the 
highwall of a surface mine during regrad- 
ing and restoration activities. These 
materials will prevent ground water from 
penetrating the highwall and entering an 
adjacent underground mine. 

The advantage of soil sealing is its 
potential effectiveness in reducing wa- 
ter infiltration. A disadvantage of soil 
sealing is that, depending on the type of 
sealant, the future use of the land may 
be severely limited for activities such 
as agriculture, industry, and recreation. 
Other disadvantages include the need for 
obtaining access to the land and the po- 
tential for aggravating downstream flood- 
ing and erosion problems by increasing 
surface runoff. 

Reported costs range widely, as 
follows: 

Concrete $42.30-$84.60 per cubic yard 

Clay.... 2.80- 8.50 per cubic yard 

Rubber.. .70- 1.40 per square foot 

Asphalt. .30- .80 per square foot 

STREAM CHANNEL MODIFICATIONS 

A stream that flows over highly perme- 
able areas may be a significant source of 
underground mine water. Such streams can 
lose water to underground mines through 
their streambeds by surface water-body 
seepage or surface water inrush. Verti- 
cal fractures and subsidence of strata 



TABLE 2. - Representative costs for surface regrading and restoring 



Item 


1975 dollars 


1980 dollars 




Per acre 


Per hectare 


Per acre 


Per hectare 


Clearing and grubbing... 
Backfilling and grading: 


$500 

2,000 

1,800 

$500- 550 

1,800-3,800 
1,500-3,400 


$1,235 

4,938 

4,445 

$1,235-1,358 

4,445-9,383 
3,704-8,395 


$700 

2,820 

2,540 

$700- 775 

2,540-5,350 
2,115-4,790 


$1,740 
6,950 




6,260 




$1,740- 1,910 


Regrading: 


6,260-13,220 




5,220-11,830 



includes lime, fertilizer, seeding, and mulch. 



Source: Scott and Hays (29). 



25 



overlying underground mines can also pro- 
vide openings through which surface 
streams can penetrate. A stream flowing 
over such areas may allow water to infil- 
trate into mines at rates 1,000 times 
higher than those of an adjacent area. 
Streams flowing through abandoned and ac- 
tive surface mines can also, owing to the 
more permeable soils at the mine, allow 
water to infiltrate the underground mine. 

Advantages of channel modification are 
the potential for a high degree of effec- 
tiveness in reducing mine water inflow, a 
long service life, low maintenance re- 
quirements, and relatively low costs com- 
pared with pumping and treating mine 
water. 

The disadvantages include the need for 
obtaining surface access to construct the 
facilities, determining the party respon- 
sible for restoring abandoned surface 
mines and subsidence areas, and the po- 
tential for aggravating downstream ero- 
sion and flooding problems. 

The costs of channel modification will 
normally be much less than pumping and 
treatment costs of an equal volume of 
mine water. The costs of channel excava- 
tion are estimated to range from $1.40 to 
$4.20 per cubic yard ($1.85 to $5.50 per 
cubic meter). Lining the channel bottom 
with clay costs from $1.40 to $2.80 per 
square yard ($1.70 to $5.10 per square 
meter). The cost of stabilizing the 
channel with riprap or with a vegetative 
cover should also be included in estimat- 
ing channel modification costs. The to- 
tal cost of reconstructing a channel is 
estimated to range from $14.00 to $35.25 
per linear foot ($46.25 to $115.60 per 
linear meter). These cost estimates are 
in 1980 dollars and are based on data de- 
veloped by Scott and Hays (29) . 

GROUTING 

The process of grouting consists of 
injecting fluid materials into perme- 
able rock and/or soil formations to fill 
pore spaces and allowing the material to 
set, forming a stiff gel or hardened 
cement-type material. The purpose of 
grouting is to reduce the permeabil- 
ity of the grouting medium by sealing 



fissures, fractures, and other permeable 
formations. 

An impermeable barrier formed by grout- 
ing is called a grout curtain. Grout 
curtains are used to control leakage 
around underground hydraulic seals, to 
stabilize outcrop areas, and to reduce 
water infiltration through subsidence 
areas and through fracture zones. Grout 
curtains are also used to reduce water 
infiltration through barrier pillars, 
around mine openings, and during shaft 
sinking by reducing the permeability in 
these areas. 

In addition, grout retainers consisting 
of large bags made from materials such as 
cloth or plastic can be placed in large 
openings (e.g., mine shafts) and filled 
with grouting materials. 

The advantages of grouting are its con- 
venience and effectiveness for sealing 
fissures, cracks, and permeable forma- 
tions. Grouting can also increase the 
strength and load-bearing properties of 
ground formations. 

The greatest disadvantage of grouting 
is its requirement for skilled labor 
knowledgeable in grouting materials, 
equipment used, and geological forma- 
tions. Additionally, some grouting mate- 
rials are toxic and present a potential 
safety hazard to personnel. 

BOREHOLE SEALING 

Boreholes are vertical or near-vertical 
holes, usually drilled during mineral ex- 
ploration activities, which are often 
used later for supplying power to under- 
ground equipment or for discharging wa- 
ter pumped from the underground mine 
workings. ^The boreholes that intercept 
mines act as conduits and are capable of 
transmitting large volumes of water to 
the mine from surface water sources and 
from overlying aquifers. 

Boreholes can be effectively plugged to 
prevent the passage of water. The bore- 
holes can be sealed by placing packers 
and injecting a cement grout, or by fill- 
ing the hole with rock over which a con- 
crete or clay plug is installed. 

When the boreholes are sealed with ce- 
ment grout, the packers should be placed 



26 



below the aquifers overlying the mine to 
prevent subsurface water infiltration. 
These packers should, however, be located 
well above the mine roof to guard against 
roof collapse from additional water pres- 
sure. Boreholes can also be sealed by 
filling the hole with rock until the mine 
void directly below the hole is filled to 
the roof, then placing successive layers 
of increasingly smaller stone above the 
rock, and installing a clay or concrete 
plug. The remainder of the hole can then 
be either filled with rock or capped. 

Boreholes can be sealed from the sur- 
face or from below in an active under- 
ground mine. It is usually more diffi- 
cult to seal a hole from the surface. In 
many instances, the holes must be cleared 
of debris prior to sealing. 

An advantage of borehole sealing is 
that the seals will prevent not only the 
passage of water into the underground 
mine but also the discharge of mine water 
pollutants from a flooded abandoned mine 
having a water level above the borehole 
elevation. An additional advantage is 
that little operation and maintenance is 
required after the sealing is complete. 

A disadvantage of borehole sealing from 
underground is that the roof strata lose 
their support as coal is removed during 
mining, which increases the danger of 
roof collapse. If roof collapse occurs, 
the sealing operation may be rendered 
ineffective. An additional potential 
disadvantage may be the determination of 
responsibility for sealing a borehole 
for an abandoned mine. Borehole sealing 
should be conducted as part of a mine 
closure and sealing program. 

During 1973, the Pennsylvania Drilling 
Co. installed a borehole seal to elimi- 
nate the flow of water from the Lower 
Freeport Coal Seam to the Lower Kittan- 
ning Coal Seam at the Tanoma Complex, 
Upper Crooked Creek, Indiana County, PA 
(29). 

The 10.25-in (26-cm) diameter borehole 
was sealed in the following steps: A 
packer was hydraulically set at 323 ft 
(98.5 m) by pumping water through a 7-in 
(17.8-cm) steel casing at pressures up 
to 1,000 lb/in'- (703,000 kg/m 2 ); cement 
grout was then pumped through ports to 
the outside of the casing until the 



cement rose to the Lower Freeport open- 
ing; a top cementing plug was then pumped 
into place; a threaded cap was placed on 
top of the casing; and a plate was tack- 
welded between the existing borehole cas- 
ing and the steel casing. 

The completed seal cost a total of 
$8,611 and successsfully stopped the 
leakage between the coal seams. 

SUBSURFACE SOIL SEALING 

Subsurface soil seals can be applied to 
control surface seepage above underground 
coal mines and in abandoned and active 
surface mines. They may also have lim- 
ited use in controlling mine subsidence 
fractures occurring near the surface. 
Subsurface seals are formed by injecting 
an impermeable material into the soil 
strata to control subsurface water move- 
ment. Materials that may be used for 
this purpose include asphalt, cement, and 
gel. Various latexes, water-soluble pol- 
ymers, and water-soluble inorganics have 
been demonstrated to be effective in lab- 
oratory and field tests. Grouting mate- 
rials injected below the surface can be 
an effective method of soil sealing; how- 
ever, in severely fractured areas, the 
grout does not fill the void space and, 
consequently, the sealing efficiency is 
reduced. 

Placing a seal below the surface has 
several advantages over using a surface 
seal: (1) A subsurface seal is less 
affected by mechanical and chemical ac- 
tions , (2) the future land use of the 
area would not be as severly restricted, 
and (3) the seal could be located in an 
area of lower natural permeability. 

The disadvantages of subsurface soil 
sealing include a significant reduction 
in sealing efficiency if the material is 
injected in a severely fractured area, 
the lack of large-scale applications dem- 
onstrating the success of this technique, 
and the need to obtain access and disturb 
the surface area overlying the mine. 

Although many laboratory and small- 
scale field tests have been conducted on 
subsurface sealants, there has been no 
full-scale application of this technique 
to demonstrate its feasibility. 



27 



MINE SEALING 

Abandoned underground mines are a po- 
tential water source to nearby active un- 
derground mines. As such, the abandoned 
mine not only contributes to the water- 
handling problems in the active mine but 
also poses a safety hazard to mine work- 
ers owing to the possibility of a sudden 
inrush of large quantities of water. 

To reduce these potential problems, the 
following preventive measures can be im- 
plemented as part of the mine closure op- 
eration: (1) leaving safety pillars or 
barriers, (2) providing a standby sub- 
merged pump facility, (3) constructing 
water dams, (4) erecting bulkhead doors, 
and (5) maintaining records concerning 
the mine. 

Implementation of these measures may 
not be entirely successful in preventing 
water from exfiltrating from the aban- 
doned mine perimeter. Pumping the mine 
water to the surface would also not be 
entirely successful if additional water 
infiltrates the abandoned mine and would, 
furthermore, incur considerable operating 
expenses. In order to effectively pre- 
vent water from escaping an abandoned 
mine, all of the potential sources of 
water exfiltration must be sealed. Mine 
sealing involves the closure of mine en- 
tries, drifts, slopes, shafts, subsidence 
holes, fractures, and any other openings. 

There are two kinds of seals that can 
be used for water seepage control: 

1. Dry seals: The purpose of dry 
seals is to prevent air and water from 
entering underground mines. These seals 
are used only when mining is in the down- 
dip direction and when there is little 
or no flow and little danger of a hydro- 
static head developing. Dry seals are 
installed in openings on the high side of 
a mine. Suitable materials for dry seals 
include masonry block, clay, concrete, 
and soil. 

2. Hydraulic seals: The purpose of 
hydraulic seals is to cause and maintain 
flooding of the mine. In hydraulic seal- 
ing, the mine creates an impoundment 
and the entire mine acts as an under- 
ground reservoir. The effectiveness of a 



hydraulic seal depends largely on the 
location of the sealing area relative to 
ground water levels and the extent of 
fracturing in the surrounding strata. 
Seals placed above ground water levels 
create a hydraulic head that the sur- 
rounding strata must be able to contain. 
If these surrounding strata contain a 
number of fractures or a good aquifer, 
the ground water flow will increase as 
the mine floods. 

The entire dam area must be able to 
withstand the water pressure, which can 
be in excess of 1,000 ft (300 m) . Miner- 
al barriers left along mineral outcrops 
and between adjacent mines are often the 
weakest link in the underground impound- 
ment. These barriers are usually of non- 
uniform thickness and frequently cannot 
withstand water pressure. ' 

The first step in hydraulic sealing is 
to conduct an examination of the geo- 
logic, hydrogeologic, and mine extent and 
condition perimeters to identify the hy- 
draulically unsound areas. These areas 
may include surface-mined outcrops, sub- 
sidence holes, boreholes, and fractured 
mineral barriers. If feasible, these 
areas should be improved by sealing or 
grouting. If this is not feasible, the 
mine pool elevation should be lowered or 
the sealing project abandoned. The ef- 
fectiveness of mine sealing is often de- 
termined primarily by the physical and 
mining framework and less by the actual 
effectiveness of the sealing technology. 

The hydraulic seals most often used for 
mine sealing are the single and double 
bulkhead seals. These seals can be made 
from concrete, quick-setting cement mate- 
rial, or grouted aggregate and are formed 
by either injecting the material through 
vertical boreholes or by placing the ma- 
terial directly within the mine opening. 
The single bulkhead seal could also be 
made from masonry block or brick. In ad- 
dition to the bulkhead seals, gunite, 
clay, and grout bags can be used to hy- 
draulically seal mine openings. 

The seals should be anchored into the 
mine openings. Additionally, to ensure 
effectiveness of the seal, a grout cur- 
tain may need to be placed directly adja- 
cent to the seal. Vertical shafts and 



28 



surface breaks can be filled with imper- 
vious materials such as compacted clay, 
earth cover, or cement. 

Mine sealing can be an effective tech- 
nique for controlling a potential water 
source for a nearby active mine. It also 
reduces potential safety hazards by re- 
ducing the possibility of a large inrush 
of water into the active mine. Another 
advantage of mine sealing is that after 
the initial capital expenditure, assuming 
that the sealing is effective, no addi- 
tional operating and maintenance costs 
would be incurred. 

The disadvantages of mine sealing are 

(1) if the roof strata lose their support 
(as a result of mining) and collapse, the 
sealing operation would be ineffective, 

(2) it is difficult to locate and, subse- 
quently, seal all of the water leaks, be- 
cause of inadequate records kept by min- 
ing companies and because of backfilling 
operations that cover evidence of frac- 
ture, and (3) seals lose their effective- 
ness with time, depending on the method 
of construction and any change in the 
strata surrounding the seal. Another 
problem is the inability to successfully 
anchor the seal into the surrounding mine 
strata, resulting in leakage around the 
seal. Other disadvantages involve sec- 
ondary effects of mine sealing. A hy- 
draulic seal placed in a mine in Pennsyl- 
vania created sufficient head to cause 
ground water levels to rise and flood 
cellars and damage foundations. The 
sealed mine was subsequently opened to 
relieve the ground water pressure. 

A double bulkhead seal was constructed 
in the drift entry of an abandoned mine 
in the Kittanning Coal Seam in West Vir- 
ginia (29). The front and rear bulkheads 
were constructed with quick-setting ce- 
ment. Grout pipes and limestone were 
placed in front of the rear bulkhead, 
which was located in front of an existing 
air seal. The limestone was stabilized 
and rendered impermeable by grouting with 
light cement. Prior to sealing, the 
average rate of discharge from the mine 
was 74 gpm (4.7 L/s). 

One week after the sealing was com- 
plete, the head behind the seal was 
3.20 ft (0.98 m) and an opening near the 



seal was observed to be leaking. After 
placing a permeable aggregate seal in 
this opening, the head behind the seal 
stabilized at 3.8 ft (1.2 m) . 

Approximately 2 yr after the sealing 
was complete, the seal was inspected. 
Although there was some flaking off of 
the front bulkhead, no seepage was ob- 
served. The total cost of constructing 
this seal was $9,463. 

A grouted, aggregate, double bulkhead 
seal was developed for sealing inaccessi- 
ble mine entries in the Middle Kittanning 
Coal Seam in Butler County, PA. Between 
February 1969 and August 1971, this seal 
was constructed in the openings of 19 
mines. 

Double bulkhead seals were constructed 
by placing coarse, dry aggregate through 
vertical drill holes and then grouting 
the boreholes to form solid seals. Water 
was pumped from the space between the 
bulkheads and replaced with a center plug 
formed by poured concrete. Curtain 
grouting was performed for a minimum of 
50 ft (15 m) from both sides of the seal 
at each mine entry. 

This sealing program had the follow- 
ing effects on mine water discharges: 
(1) Eight mines had no flow, (2) one mine 
had an average flow less than 1 gpm (0.06 
L/s), (3) eight mines had reduced flow 
rates, (4) one mine had the same flow 
rate, and (5) one mine had a 1.5-gpm 
(0.095-L/s) increase in flow rate. 

The water level in the mines ranged 
from 1 to 5 ft (0.3 to 1.5 m) , which 
fluctuated with precipitation and in- 
filtration. The head behind the seals 
ranged from less than 1 ft (0.3 m) up to 
38 ft (11.6 m). 

The costs of the seals ranged from 
$8,308 to $58,437, with an average cost 
of $19,480 per seal. Approximately 61 
pet of this cost was attributable to cur- 
tain grouting. Representative costs for 
constructing various types of mine seals 
are shown in table 3. 

WELL DEW ATE RING 

Aquifers situated both above and di- 
rectly below an underground mine are po- 
tential sources of water infiltration 



29 



TABLE 3. - Representative costs for construct 

Seals 

DRY SEALS 

Masonry block 

Placement of clay seals 

Construction of clay bulkheads 

HYDRAULIC SEALS 
Double bulkhead seals: 

Grouted aggregate (with grout curtain) 

Quick-setting (no grouting) 

Grouting around seal and curtain grouting of 
adjacent strata. 

Single bulkhead seals (with grouting) 

Gunite seals 

Clay seals 

Grout bagseals 

Shaft seals: 

Backfilling shafts [from 100 to 300 ft (30 to 
100 m)]. 

Concrete seals 

Gel materials (AM-9 chemical grout) 

Curtain grouting: 

Vertical curtains 

Horizontal curtains 



ing various types of mine seals 



Est. 1980 dollars 



Per 



$3,520 -$4,230 

2.80- 5.60 
3.70- 7.40 
3,520 - 6,340 



14,100 


-42,270 


21,150 


-25,360 




28,180 


7,050 


-14,100 




18,300 


2,800 


- 5,600 


14,100 


-21,150 


9,860 


-49,300 


28,200 


-35,200 




12,700 


49 


113 


160 


370 


16,900 


-28,200 


41,750 


-69,600 



Seal. 

Cubic yard. 
Cubic meter, 
Seal. 



Do. 
Do. 

Do. 

Do. 
Do. 
Do. 
Do. 

Do. 

Do. 
Do. 

Linear foot. 
Linear meter, 
Acre. 
Hectare. 



Source: Scott and Hays (29). 



into the mine. In addition, joint sys- 
tems, faults, fracture zones, and subsi- 
dence fractures can be potential sources 
of water in an underground mine. To re- 
duce these potential water infiltration 
sources, well dewatering sysems have been 
suggested to intercept the aquifers and 
to control the movement and ultimate dis- 
charge of the ground water. 

Three basic well dewatering systems 
have been suggested in documented lit- 
erature. These systems are (1) ground 
water pumping directly to the surface, 

(2) gravity drainage to the mine, with 
subsequent discharge at the surface, and 

(3) gravity drainage into underlying 
aquifers. These systems, which are all 
in a developmental stage, are discussed 
in greater detail below. 

Ground Water Pumping Directly 
to the Surface 

This type of well dewatering sys- 
tem, which is illustrated in figure 3, 



involves installation of closely spaced 
wells that are drilled from the land 
surface and tap aquifers lying above and 
below the mine. The wells are cased 
above the source bed. The ground water 
is then pumped to the surface and can be 
either discharged to a nearby stream or 
used for water supply purposes. Since 
the ground water does not enter the mine 
environment, the quality of the water is 
maintained and treatment should not be 
required. 

In figure 3, ground water pumping sys- 
tems are illustrated for dewatering aqui- 
fers located above and below the mine. 
In the cases shown, it would not be fea- 
sible to try to force the water into low- 
er rock units. 

Gravity Drainage to the Mine 

This system, which is illustrated in 
figure 4, is similar to the ground water 
pumping system except that the ground wa- 
ter drains by gravity to the underground 



30 



Surface, 



Initial water level 






£fe 




Confining 
bed 



— »- Deep mine 



Source beds located above deep mines 



-Deep mine in regional 
ground water discharge 








^r!vl-i— r 4^l:"U-^".. 'Source bed 



Source beds below mines located in ground water 
discharge areas 

FIGURE 3. - Ground water pumping systems. 

mine and is then pumped to the surface 
for disposal. This system eliminates the 
need for a pump in each dewatering well. 
Instead, it requires a central collection 
and pumping system within the mine, which 
is already common practice in many under- 
ground mines. The collection and con- 
veyance system, however, would consist 
of a piping arrangement whereby the water 
would not come into contact with the 
pyrite-bearing rock and would, conse- 
quently, not require treatment prior to 
discharge. 

In updip mining from drift or slope en- 
tries, a gravity drainage system could be 
installed whereby the overlying aquifer 
is drained into the mine and the water is 
drained by gravity to the slope of the 
drift opening. 



Surface 



'.'•■.—" i*?-:-;— *| |*7- :: -*i i*t" Source bed-'. ■■■'A 
•" ' •'."•'■• I . !■"•'•'■ ••:••■"•' ■ [■'■'■' '■ ■'••■'!■ !• ■•.'. : . '••.-•'-■ ■•':'■■.'•. ■-. : 



[Confining bed ■..'•, ■ 



i\ Seepage 
face 



— Mine 
drainage 



FIGURE 4. - Gravity drainage into mine. 
Gravity Drainage Into Lower Aquifers 

This system, shown in figure 5, is sim- 
ilar to the ground water pumping system 
except that the ground water drains by 
gravity through wells drilled through the 
underground mine and, eventually, into a 
deeper aquifer. The mine roof rock and 
the mine opening should be cased and 
grouted to prevent water from entering 
the mine and to prevent contaminated mine 
water from entering the underlying aqui- 
fer. Double casings and grout may be 
needed to prevent corrosion of the steel 
casing within the mine. 

This system requires the availability 
of favorable geologic conditions reason- 
ably close to the mine area. Both a re- 
gional recharge area and a deep aquifer 
system have to be present for the system 
to work. A hydrogeologic setting where 
two to three distinct water tables and 
rock beds occur is ideal. The ground wa- 
ter flow must be downward. This system 
is not feasible for high fluid volumes in 
excess of 3 million gpd (130 L/s). In 
the Appalachian region, this factor alone 
may create limitations, as the aquifer 
must be capable of accepting the antici- 
pated flow. 

A possible alternative to installing 
separate dewatering systems for each mine 
would be to construct a regional drainage 
system designed to reduce the flow of wa- 
ter into several mines within a given 
drainage basin. One such system, the 



31 



Surface 




FIGURE 5. 
aquifers. 



Gravity drainage into underlying 



Hoffman Tunnel, was constructed in the 
Georges Creek Basin water province in Al- 
legany County, MD [Slaughter and Darling 
(33)]. 

The Hoffman Tunnel, which was con- 
structed in the early 1900' s to drain the 
Pittsburgh Coal Seam, has a total length 
of 10,646 ft (3,245 m) with approximately 
2,600 ft (800 m) of auxiliary tunnels and 
26,700 ft (8,100 m) of ditches draining 
to it. The drainage area covers roughly 
14 mi /i (36 km ? -) , which extends north from 
Midland to Zihlman. The mean flow of the 
tunnel in the late 1950' s averaged about 
940,000 gpd/mi 2 (16 L/s for each square 
kilometer of surface area) . During low- 
flow periods , the tunnel can divert near- 
ly all of the flow of the upper third of 
Georges Creek, which is a tributary of 
the Potomac River. 

The potential benefit of well dewater- 
ing systems is that they are preventa- 
tive, rather than prescriptive, tech- 
niques that rely on natural geochemical 
and hydrogeological systems. Other ad- 
vantages are a reduction in the amount 
of mine water that must be treated and 
a possible reduction in pumping and 



maintenance costs. Additionally, if the 
local need for water becomes sufficient 
in the future, the dewatering wells can 
be converted to water supply wells. 

Well dewatering systems are still in 
the developmental stage, and large-scale 
applications of these systems have not 
been shown to be cost effective in the 
United States. Since it is usually not 
possible to completely eliminate water 
infiltration into the mine, the dewater- 
ing system just reduces, does not elimi- 
nate, the water-handling requirements in 
the mine. Depending on the character of 
the rock, a dewatering system may not 
produce noticeable results for more than 
a few hundred feet from the wells and it 
may take several months before results 
are noticed. 

Prior to implementing a dewatering sys- 
tem, the impact on neighboring land uses 
must be considered. If the system will 
threaten local water supplies, the yield 
of the well system must either be reduced 
or used to supplement the water supply. 
The possibility of well plugging is 
another potential problem. If the aqui- 
fer contains ferrous iron, precipitation 
of iron oxyhydroxide and growth of iron- 
oxidizing bacteria around the wells could 
reduce the permeability of the aquifer 
and decrease well efficiency. 

Costs 

The cost effectiveness of a well dewa- 
tering system will depend on a comparison 
of the cost of pumping and treating mine 
water with the cost of the dewatering 
system. The cost of a dewatering system 
will depend on the the number and spacing 
of wells, the well depth and diameter, 
casing requirements, and depth to static 
and pumping levels. The cost will in- 
clude hydrogeologic evaluations, drill- 
ing, casing, piping, and possibly grout- 
ing to control leakage through the mine 
roof. 

The total annual costs per well in dol- 
lars per million gallons of water a day 
delivered to the surface are estimated as 
follows: 



32 



Well yield, gpm 

75 , 

230 , 

760 , 



Annual cost, 
per million gpd 

$36,970 
19,460 
13,430 



These estimates assume a 25-yr service 
life for the well and equipment. 

Mine water treatment costs are esti- 
mated to range from $0.10 to $2.45 per 
1,000 gal ($0.02 to $0.64 per 1,000 L) 
depending on the water quality and on the 
effluent discharge limitations. The low- 
er estimate is for water containing 2 
to 3 ppm iron and up to 20 ppm acidity. 
The higher estimate is for water with 500 
to 700 ppm iron and 2,000 to 5,000 ppm 
acidity. 

The cost estimates in this section were 
taken from a Pennsylvania State Univer- 
sity research report prepared by Parizek 
(23) , and adjusted to 1980 dollars. 

Case Study 

A pilot dewatering program was con- 
ducted at the site of the Lancashire No. 
20 Mine, near Carrolltown, PA (38). The 
objectives of this program were to assess 
the impact of a well dewatering program 
on the quantity and quality of mine water 
inflows, to evaluate the potential effec- 
tiveness of the well dewatering tech- 
nique, and to conduct an economic evalu- 
ation of the program. 

A total of seven wells were drilled and 
used for dewatering. A pumped-well sys- 
tem was selected for dewatering because 
pumped wells provide more information and 
create fewer mining disruptions and safe- 
ty hazards than the other dewatering sys- 
tems considered. 

Some of the conclusions of this program 
were — 

1. Fracture-dominated flow systems 
usually prevail where large mine water 
inflows are experienced. Ground water 



flows into the subject mine were concen- 
trated along two fracture zones that 
appeared to intersect at the area of 
greatest inflow. 

2. Flows responded rapidly to wet and 
dry periods in spite of the 500-ft (152- 
m) mine depth, indicating that the frac- 
ture zones had hydraulic connections to 
the surface. 

3. Dewatering with three wells was 
performed continuously for 14 days with 
an average well effectiveness, initially, 
of 45 pet (i.e., 45 pet of the pumped wa- 
ter was diverted from mine inflow). The 
average well effectiveness increased to 
55 pet at the end of the test, and it was 
projected that it would increase to 80 
pet after 120 days of pumping with no re- 
charge. The well effectiveness for full- 
scale mine dewatering was estimated to 
range from 50 to 80 pet. 

4. The wells in this study were not 
cost effective unless the average well 
yield was increased from 3 to 4 times. 
The cost of well dewatering was estimated 
to be at least twice as great as water 
removal and treatment costs. If, how- 
ever, the acidity of the mine water were 
higher, i.e., 500 to 1,500 ppm (500 to 
1,500 mg/L) and if the coal seam were 
less than 150 ft (45 m) deep, the dewa- 
tering system would have been cost ef- 
fective. Three significant variables in 
the cost comparison were depth of the 
well system, the acidity level of the wa- 
ter, and ground water flow patterns. 
Additionally, if the wells had been lo- 
cated along the fracture zones, a higher 
well yield could have been obtained, 
which would have increased the cost ef- 
fectiveness of the dewatering system. 
The cost-effectiveness analysis did not 
consider the indirect benefits of dewa- 
tering (e.g., increase in productivity, 
more stable roofs, and reduced safety 
hazards) . 



SUMMARY OF WATER CONTROL PRACTICES 



Table 4 is a summary of the water con- 
trol practices previously discussed. 
(The siting of surface facilities and 



openings is not included because there is 
not enough information on this practice 
as a method of controlling water inflow.) 



33 



Table 5 shows equivalent water control 
costs. These tables list information on 
each practice's applicability, limits of 
control, field experience, and costs. 
The limits of control and the field ex- 
perience taken together give an indica- 
tion of each practice's effectiveness. 
Thus, a preliminary attempt can be made 
to assess the cost effectiveness of most 
of the control practices listed. This is 
important since it is the cost effective- 
ness of a control method for a given sit- 
uation that should determine the choice 
of that measure. 

As indicated in table 4, all of the 
surface control measures listed and all 
but two of the ground water control mea- 
sures have some information available re- 
garding their cost effectiveness in con- 
trolling inflow into underground mines. 
Only subsurface soil sealing and well 
dewatering lack sufficient data on 
effectiveness . 



Of the control practices that have 
available performance information, only 
soil sealing is considered to be unsatis- 
factory. The performance data on soil 
sealing indicate that its use would be 
very costly, on the order of $30,500 to 
$61,000 to seal an acre of land with rub- 
ber. This should be compared with sur- 
face regrading and restoring, which costs 
roughly $1,800 to $3,800 for the equiva- 
lent conditions of applicability. Al- 
though the literature evaluation has pro- 
vided information on the effectiveness of 
these practices in controlling water in- 
flow in underground coal mines, a quanti- 
tative analysis is needed to accurately 
determine the cost effectiveness of these 
measures. The quantitative analysis 
should include the benefits and drawbacks 
associated with the use of each prac- 
tice, taking into account factors such as 
health and safety, the environment, and 
production. 



ANALYSIS OF THREE WATER CONTROL PROJECTS 



The water control practices considered 
for evaluation were identified through a 
combination of literature review and per- 
sonal conversations with a large number 
of knowledgeable individuals, State and 
Federal agencies, and private and public 
organizations associated with the coal 
mining industry. These water control 
practices have been described in the pre- 
ceding sections. It must be emphasized, 
however, that most of these practices 
have been used principally to control wa- 
ter problems associated with abandoned 
coal mines. 

Discussions with personnel of both 
State agencies and mining companies in 
Appalachia made it very clear that the 
only widely accepted method of dewater- 
ing underground coal mines is to collect 
the water in sumps and pump it up to the 
surface, where treatment is provided, as 
needed, prior to discharge to receiving 
streams. Personnel of both the State 
regulatory agencies and mining companies 
indicated very limited, if any, knowledge 
of the application of dewatering tech- 
niques in advance of mining in the Appa- 
lachian coalfields. In fact, the inves- 
tigations identified only three cases 



where dewatering in advance of mining was 
either being considered or applied. 

Of these three cases, only one repre- 
sented an actual documented demonstration 
of the feasibility of dewatering in ad- 
vance of mining. This particular demon- 
stration evaluated an attempt to dewater 
a section of a mine using a series of de- 
watering wells drilled from the surface. 

The second of the three cases was a 
preliminary feasibility study to deter- 
mine whether dewatering in advance of 
mining using dewatering wells would be 
technically and economically feasible for 
a new mining operation. 

The third case represents an ongoing 
attempt to control water problems in the 
last working section of an old mine. 
Subsidence is being induced in the area 
of heaviest inflow in order to concen- 
trate the mine drainage in a system of 
sumps, which will then allow the safe ex- 
traction of the remaining coal. 

The three case studies differed marked- 
ly. Case study 1 was a federally funded 
demonstration project, which spanned a 
period of approximately 33 months. This 
study provides the most comprehensive and 
detailed data available to date on the 



34 



















































1 




• 


O 


CO 

3 




• 








>, 
















co 


















OJ 








Sh 


3 


bO 


4-1 


0) 


4= 


CD 








3 
















3 >% 


















rO 








3 


o 


3 




Vj 


CJ 


4-J 




0) 




cO 


M 


• 










i 


d co co 


























CJ 


rH 


•H 


13 


3 


3 


3 




CJ 




d 


c 


CO 










CO 


















O 










MH 


4^ 


0) 




CO 


iH 




c 






■H 


CO 










a 


> 3 




Sh 














4-J 








3 


3 


3 


CO 


13 




O 




<u 




3 


>> 


CO 










CD 


•H ID 1 


O 


CO 


3 










• 








•H 


•H 


•rH 


3 


CO 


3 


'I - ) 




■H 




•H 


M 


CJ 










CU 


4-J 


4-» 


0) 










3 QJ 












CO 




N 


o 






S-i 






CO 


CJ 












Sh hO 




3 


co 










QJ > 








CO 


Sh 




3 


•iH 


r-H 


•3 




cu 




•3 


> 


3 










-3 


4-J >4H 


0) 


5 


x> 










> -H 








> 


3 


4H 


CO 


rH 


Mh 


3 




ex 




0) 




CO 










CO 


CO 3 "H 


3 
















O 4-1 








•H 


4H 


MH 


0) 


3 


3 


3 




X 




CO 


X 












CO 


CO 


13 


MH 


• CD 










Sh CJ 








4-J 


3 


3 


43 


CJ 


•H 






01 




3 


4-1 


<4H 










3 


4-1 U CO 




O 


CO 3 










CX 3 








CJ 


3 4= 




o 




CO 










•rH 


o 












cO > 


CO 




3 J3 • 










MH 








CO 




CO 


o 


rH 


Sh 


4-J 




XI 




3 


3 












3 


•H 


■H 


bO 


•H 


13 










3 MH 








MH 


bD 




CO 




0) 


rH 




iH 




0) 




CO 










CO 


>, • 4-J 




3 


d CD CO 










CO QJ 








MH 


3 


bO rH 


4-1 


4-J 


3 




0> 




OJ 


co 


.H 










CO 


i-l CO CJ 


Sj 


•H 


CD 4-» 










CO 








CO 


•H 


3 


3 


3 


3 


CO 




•H 




43 


OJ 


cu 










Xi 


i-H CO CU 


CO 


•3 


Sh CO -H 
CO CJ d 










X S^ 










rH 


•rH 




0) 


3 


MH 




fe 






co 


> 












CO 4-J MH 


4J 


3 










r4 








>. 


•H 


Sh 


CO 


d 












CO 


cO 


OJ 










CO 


•H -H <4H 


3 


o 


> CJ -H 










CD 3 








Sh 


CO 


3 


eS 


0) 


MH 


CO 








s 


CJ 


r-\ 










JS 


O CO CO 


is 


a. 


O 3 rH 










3 > 








CU 


4-1 


13 


CJ 


O 


3 




















in 








C/3 










EC 








> 




























T3 
















3 






































1 


c 






O 








*. 








•H 




>^ 






CD 










** 


















C 


o 


CU 


1 


43 






cu 


3 










Sh 


rH 


>-. 




CO 










CO 


















•H 


•H 

4-J 


c 

1 


a 

CO 


4J 

9J 






bO 
cO 


O O >, 
•H 4-J CO 






O CU 
4-J > 


QJ 


rH 
3 


3 
S3 




•H 

4-1 3 








bO 
3 


4-J 

•H 


















OJ 


CO 




d 


S 




3 


4-J 3 Q 


1 




3 -H 


4J 


3 






•H 








iH 


3 














i-H 




s 


u 




CO 








•H 


CO -H 


3 




•iH 4J 


o 


CO 




• 


4-J bO 








4-J 


13 














O 




1 


4-> 


MH 


> 


*> 






CO 


4-J 13 


•H 






CJ 




3 


• 


CU 


3 3 








•H 


3 












CD 


U 




rH 


H 


CO 


CO 


• 


• 


SH 


•rA C G 






3 CU 


Sh 




3 


co 


3 iH 








d 


O 












CU 


4-1 






•H 




4= 


0) 


0) 


3 


13 


a- o co 


>% 




O <4H 


O 


4-> 


O 


3 


3 rJ 








•H 


CJ 












CJ 


3 




MH 


14H 






CJ 


rH 


o 




•H -rH rH 


I 


• 


•rH MH 




O 


•rH 




cr co 








rH 




• 










•H 


O 




•H 


G 


• 


4-> 


cO 


X 


rH 


MH 


CJ 4-> 


3 


4-J CO 


CO 


rZ 


4-J 


13 


4J 










4J 


CO 










4-J 


u 






•H 


a) 


o 


MH 


■H 


■a 


o 


CO cO O 




o 


3 


co 




3 


3 


0) 3 








3 


CJ 


CO 










CJ 






0) 




o 


3 


i-J 


co 




M M 4J 




rH 


i-4 4-> 


Sh 




rH 


3 


bo o; 








•H 


01 


Sh 










CO 


14-1 




> 


O 


CO 




3 


cO 


CO 


0) 


a. 4-> 


• 


% 


■u o 


3 


• 


O 


rH 


Sh 










Sh 


3 










u 


o 




•W 


4-1 


<4H 


CO 


co 


0) 


CU 


to 


rH CO 


CO 


rH IZ 


4-1 


CO 


CO 




3 d 








3 


•H 


4-J 










CX 






4-J 




r4 


OJ 




<4H 


M 


•H 


rH -H CO 


CO 


3 


•H 


CJ 


4-J 




0) 


rH O 








> 


13 


o 












CD 




CJ 


a) 


3 


o 


CU 




4-1 


CO 


«0 <4H CO 


0) 


0) 


MH 


3 


■H 


d 


S-i 


Sh 








iH 




3 










i-H 


4-J 




CU 


3 


CO 


T) 


£ 


0) 


CO 




3 3 CJ 


CJ 


Sh 


3 • 


U 


3 


>H 


3 


4-J MH 








4-1 


CO 


Sh 










O 


•H 




MH 


13 






4-) 


43 




3 


G -<-\ o 


CJ 


4-J 


•H >,M- 


13 


0) 


4J 


3 








O 


•H 


MH 










U 


e 




MH 




0) 


Sh 






0) 


o 


G < 


3 


CO 




rH 




3 


4-J 


3 


CO u 








CU 


> 












4-j 


•H 




3 


CO 


4= 


o 


o 


4-J 


CO 




CO UH 


co 




CD 3 


bO 


O 


1 


Mh 


> 0) 








MH 




co 










c 


r-1 






•H 


4-1 


4-J 


4-J 


o 


CO 


CO 


o 




CO 


4J O 


3 


CJ 


bO 




OJ 4-J 








MH 


3 


3 










o 






co 






cO 




3 


QJ 


13 


* • 


4-) 


CD 


3 


•H 




3 


4J 


Sh CO 


• 






CU 


o 












o 






43 


3 


d 


u 


CO 




S-i 


3 


CO OJ rH 


1 


3 


CO <-A 


rH 


3 


O 


1 


cx 3 


OJ 








r-H 


4= 


















o 


o 


CO 


CO 


>^ 


CJ 


CO 


CO 4-J -H 


CO 


> -H 


3 


o 


rH 




3 






4-J 


MH 


CJ 










In 






3 


rH 


M 


CX 


QJ 


crt 


3 


ex 


U cO O 


•H 


Sh 


co o 


CO 


^ 




•H 


3 MH 


•g 






CO 


3 


3 










a; 






cO 


MH 


MH 


o 


CJ 


d 


•rH 


co 


CO Sh CO 


rH 


CJ 


Sh CO 


CO 


MH 


3 


rH 


3 O 






O 


•H 


CO 










4-1 
CO 






cj 














O 








Pj 










U 








X 














3 

4-1 










1 






























d co 


1 

•H 


• 




1 


1 












O 










ex 

•H 






























O 3 
Sh 0) 


CD 


>> 
4-J 




Sh 
CO 


CO 
■H 


Sh 

CO 










>> 






o 


1 


M 




* 






I 


•3 






O 










MH Sh 


3 


•H 




> 


MH 


4= 










i-t 






4-1 


4-) 


4-J 


OJ 


CO 






d 


>, 3 






4-1 










3 


co 


rH 




O 




4-> 










CtJ 






3 
•H 


3 
O 


CO 


CJ 

CO 


cO 






•H 


i-H CO CO 
X! O rH 






3 

•rH 










CD 

CO 3 


« 


•H 
4h 




MH 


bO 
3 


o 










§ 










•» 


<4H 


!-■ 


CO 




T3 


bO cO 


















3 -H 


CO 


3 




O 


•rH 


13 


• 








3 


>, 




3 


A 


CO 


U 


CO 


<4H 




3 


•rl <4H QJ 






3 










s >-. 


CO 


o> 






rH 


3 


CO 








C/D 


4-J 




o 


CO 


CU 


3 




u 




cO 


EC U bO 






O 










S-i 


g 




>s 


3 


3 


3 










•H 




iH 


bO 


rJ 


co 


0) 


3 






3 >H 






•rH 










i-H 


3 


Sh 




4-J 


CO 




o 








I 


^H 




4-J 


3 


3 




CJ 


CO 




bO 


CO CO 






4-) 










O rH 


4-1 


CO 




•H 


CO 


*> 


•H 










•i-l 




CO 


•H 


CO 


•» 


c 






3 


• r-f 






3 bO 










4-t 3 


CJ 


cx 




rH 




co 


4-J 








• 


XI 




Sh 


c 


CO 


CO 


a) 


T3 




•H 


OJ iH 






Sh 3 










•rH 


3 






•H 


>, 


CO 


3j 








<f 


3 




4-J 


OJ 


•H 


3 


T5 


QJ 




13 


bO 3 U 






4-> -H 










3 cj 


Sh 


43 




43 


4h 


Sh 


g 










o 




i-H 


cxmh 


•H 


tH 


t3 




3 


CO CU CU 


• 




rH CJ 


• 








o co 


MH 


bO 




3 




3 


Sh 








W 


•H 




•H 


o 




1 


CO 


cO 




O 


G G £. 


CO 




•H 3 


^ 








rH CX 




•rH 




CO 


CO 


4-J 


O 








hJ 


rH 




MH 




r*2 


QJ 


X 


u 




a 


•iH 4-1 


CO 




MH 13 


4-J 








MH CD 


rH 


4= 




d 


4-J 


CJ 


MH 








PQ 


a 




g 


CO 


o 


> 


3 


bO 






CO OJ O 


CJ 




3 CO 


•H 








3 3 


3 






Sh 


3 


3 










<3 


9- 




•H 


G 


o 


CO 


co 


cu 




CO 


U rH 


3 




•rH Sh 


rH 








•rH 


CJ 


Sh 




3 


Sh 


Sh 


CO 








H 


< 






1 


(-1 


CJ 




i-i 




0) 


13 X Sh 


3 








•H 








~ 


•H 


O 




a 


4-J 


MH 


rH 














CO 






^ 


3 




4-J 


CO O 


X 




CD >> X 








CD CD 


4-1 








CO 




43 














4J 




•> 


•> 


CO 


O 


• 


cO 


CO CJ 


Sh 




4-J X 


3 








*j d 


Sh 


•> 




CD 




•> 


CO 














3 


a 


CO 


CO 


X 


3 


CO 


3 


CO -H CO 


3 




3 


CU 








3 3 


0) 


0) 




3 


bO 


CO 


5! 














CO 


rH 


a 


bO 


o 




01 


1 


> rH CO 


4-J 




co f-\ 


M 








Q) <o 


> 


CJ 




CJ 


3 


0) 


d 














> 


•H 


o 


3 


CO 


T3 


3 


o a. 3 


CO 




> i-i 


i-l 








> S-i 




3 




3 


•H 


Sh 


Sh 














3 


O 


r4 


•H 


1-1 


3 


•H 


•H 


Sh CX-H 


•rH 







O 


CO 








CO 4J 


MH 


CO 




13 


^ 


3 


3 














u 


CO 


cj 


a, 


CJ 


cO 


a 


rH 


a- co d 


-d 




s- 


CO 


ex 








Sh CD 


O 


13 




CO 


rH 


co 


CX 














a- 














W 








p. 












Pm 








Pi 


















, . 


• 














13 




























bO 
















0) 


CO 


• 














3 


























• • 


3 
















o 


rH 


• 














cO 


























co 


•H 
















•r4 


o 


• 








































r~\ 


4-J 
















4-J 


u 


• 














bO 


























O 


3 
















o 


4-J 


s 














3 


























Sh 


O 
















3 


c 


o 














•H 


























4-J 


Sh 
















M 


o 


•H 














X) 




















<-{ . 






3 


bO 
















ex 


CJ 


CO 
Sh 














cO 

u 








b 


D 










3 3 
3 O 






o 

CJ 


-3 
















rH 


Sh 


co 














bO 


• 






e 












3 -H 








3 
















o 


co 


> 














QJ 


bO 






i- 












3 4-J 






Sh 


3 


• 














u 


4-) 


•H 














IH 


3 






r- 












42 3 






0) 




CO 














4-J 


CO 


13 
















•H 






CC 












CJ O 






4-J 


bO 


3 














c 


3 
















OJ 


S-i 






a 












•H 






CO 


3 


•i-l 














o 




MH 














o 


O 






CO 












MH 






3 


•rH 


3 














o 


CJ 


MH 

o 














cO 

<4H 


4J 
CD 






r- 












3 -H 
CO 13 






13 


4-J 

3 


4-> 
Sh 














SH 


CO 


g 














)H 


CO 






•H 












Sh O 






3 


O 


3 














a> 


<4H 


3 














3 


Sh 






a 












■u d 






3 


Sh 


CJ 














4-1 


r4 


Pd 














&0 








U3 












C/5 






O 


CJ 
















CO 


3 










































Sh 


















s 


C/j 










































CJ 

















35 

































bo 


























1 

<U 




CO 


•H 












1 


3 
















CD 










1 


c 






















1 


-d 


Li 




4-1 






1 








cu o 














1 


CO 










cu 


•H 


TJ 




















s 


OJ 






c 


— 1 




CO 


C 






L H 












<D 


c 


CU 


• 








Li 


4J 


CU 




















1-1 


CD 


QJ 




OJ 


rH 


• 


CJ 


CU 








U-l 












r-l 


o 


CJ 


cu 










CO 


C 


CU 


















iH 


3 


X 


1 


e 


•H 


0) 


•H 


cu 






c c 


X 










CO 


E 


CJ 


3 








c 


c 


o 


> 






















4J 


u 


cu 


4-J 


bO rH 


X 


4-J 




i-l i-l 


b: 










CJ 


i 


3 


cr 








•H 


1-1 


— 


•H 


















C 


C 




a) 


Ll 


CJ^ 


tO 


PL. 




CO 








3 










CO 


T3 


W 


tH 










e 


c 


4-) 


















CU 


CU 


FS 


4-1 


•H 




4-1 


a. 


4J 


O 




i) 4J 


O 










1 






C 








CU 


•H 


cO 


CJ 


















OJ 


cu 


•H 


CC 


3 




CO 


CO" 


o 


CJ 




> u 


u 










0) 


CO 


CU 


XI 








> 


rH 


X 


CO 


















X 


X 




3 


O- 


• 






c 






f( 0) 


x 










bO 


c 


X 


o 








•H 


CU 


CO 
























>, 




01 


QJ 


J- 1 


CU 




OJ 




4J L 


u 


• 








u 


o 


4-1 


cu 








4J 






O 


















CD 


CD 


r4 


U4 


u 


C 


c 


H 


cu 


X 


• 


CJ 1-1 




CO 








CO 


•H 




4-> 








CJ 


Li 


e 


4J 


















CO 


CO 


Hi 


O 




1 


cu 


tfl 


> 




OJ 


a> -a 


CO 


U 








PH 


4J 


bO 










CU 


O 


o 


c 


















X 


X 


> 




bO 


E 


o 


cO 


o 


> 


U-l 


w 


i-H 










CO 


e 


CD 








U-l 




Li 


•H 






















•H 


c 


d 




cx 


CO 


X 


4-1 


•i-i 


u-i bC 


c 


O 








U-l 


O 


t4 


i-l 








U-l 


bO u-i 




• 
















CD 




4J 


o 


•H 


OJ 


o 


1 






4-1 


<u c 


•g 


_-; 








o 


•H 


4J 


X 








CU 


C 




00 


CD 
















CD 


• 


CJ 


•r-l 


r-l 


X 


rH 


QJ 


CO 


c 


CJ 




i-( 


a> 










iH 


CO 


4J 










•H 


5 


OJ 


a' 
















OJ 


-a 


CU 


4_) 


-o 


4-J 


OJ 


bO 


c 


3 


a) 


>> CJ 




Ll 








*■ 


a 


l-l 










>> 


o 


O 


c 


c 
















CJ 


OJ 


U-l 


CJ 


c 




> 


U 


o 


O 


U-l 


M 3 


o 


o 








CJ 


a 


4-1 


U-l 








Li 


3 


rH 


•d 


















CJ 


4J 


U-l 


3 


CO 


c 


ai 


cO 


■H 


X 


U-l 


CJ -O 


4J 


— 








CO 


CO 


CO 


O 








QJ 


T3 


IXJ 


E E 
















3 


•H 


CU 


X) 


X 


•r-l 


t3 


rJ 


4-' 


CO 


0) 


> 












J 














> 
























C/J 


























4-J 










1 




4-1 








































>i 
















QJ TJ 


■H 




i-i 






U-l 


to 


CO 


CO 


1 








0) 












1 




1 










>. 


cfl 








1 








X H 




I 


o 






i-l 


CU 


- 


OJ 


tH 








X 


1 


1 




• 




cu 


CO 


> 










rH 


s 


1 


1 




QJ 










3 


* 


Li 


U-l 






C 


I-l 


T 


u 


to 








4-> 


U-l 


CU 




00 


Li 


u 


1— 1 


OJ 


l 




1 


1 


X 




cu 


c 


• 


X 


• 






>, l 


O 


- 




c 




bC 


CO 




tO 


cu 






0) 




CU 


*c 




OJ 


O 




cO 


r-l 


Ll 




i—i 


O 


CO 




Li 


3 


CO 




-o 








i _c 


CD 


4-) 


11 


CO 




•H 








CO 






X 


U-l 






c 


box 


•> 


OJ 




3 




i-i 


QJ 


C 


• 




X 


H 


CD 


QJ 








: CO 


< 


CU 


1— 1 






(0 


OJ 


• 


0) 










•H 


CO 


M 


o 


c 


o 


CT? 


CO 


Ll 


CO 




cO 


bO 


o 


CO 


QJ 




r-l 


X 


CJ 










TJ 


X 


U-l 






x 


"O 


CJ 


4-1 


cu 




>, 




4-1 


OJ 


•H 


CO 


c 


4-1 




CU 






> 




CO 


cu 


r-l 


3 


QJ 


4-1 


•H 






C 0) 






1-1 


O 




CO 


4-1 


cu 


CO 


CD 


X 




eg 


CU 


•H 


E 


4-J 


X 


fl 


tO 




4J 


&C- 




cO 


CU 


CO 


rJ 


X 


cu 


3 


c 


4J 






o > 




O 


CO 






•H 




l-l 


U-l 


o 






@ 


> 




•H 


o 


CJ 




Li 


• 


a) 


c 






rH 


OJ 


cO 


cc 


U-l 




g 


o 






-J •** 


• 


4J 


c 


0) 






U-l 


3 


l-l 


s 


o 






•H 


BO 


4-1 


3 




o 


4-1 


<u 


3 


•H 




CU 


X 


Li 




QJ 




QJ 


£ 


c 






4J J-l 


a> 




o 


1—1 




>, 


iH 


4J 


3 




4J 




CO 


J-> 


OJ 




L 


CO 


4J 


CO 


bO 




CO 




X 


tO 




QJ 


o 


ccj 


X 










CO cj 


CO 


4-1 


p. 


o 




CJ 




CJ 


CO 








c 


O 


CO 


X 


4-J 


4-J 






CO 


T3 


3 




4J 


Li 


CD 


C 


•r-l 




4-) 


rH 


OJ 






L 


i 0) 


a i-i 


CD 


rj 


• 


c 


*o 


to 




• 


•o 




O 


CU 


o 


4-> 


00 


CO 


4-> 


CU 


.2 


C 


cti 






o 


c 


1 


4J 


C 




ct) 


L 






01 u-i 


CO 


3 


d) 


a> 


cu 


0) 


a> 


Li 


o 


cu 


CU 




•H 


U-l 


iH 


•H 


c 


U 


H 


C 


CO 


3 


CJ 




CO 


> 


o 


o 


cd 


E 


Li 


0? 






a. u-i 


•—I 


O 


I-l 


u 


d 


•H 


CJ 


U-l 


4J 


c 


bO 


• 


4J 


U-l 




3 





4-1 


3 


1 


OJ 


O 






cu 


CTJ 


•H 




c 


X 


o 


CU 








c 


a) 


i— i 


i-l 




o 


i-i 


o 


fl 






1 


•a 


1— 1 


cO 


0) 


S 




o 


CO 


CJ 


1-1 


l-i 


m 


• 


Ll 


U-l 


4-) 


QJ 




4J 


Li 


> 


CO 








c 


o 


U-l 


CO 


X 


E 


1-1 


T3 


>1 


CO 


3 


ct 


Li 


c 


3 


09 






1-1 






bO 


CU 


a> 


•H 




•H 


X 


QJ 




U-l 


QJ 


4J 






bo •< 


u 


U-l 


1-1 






U-l 


CU 


1—1 


CO 




1-) 


CJ 


<i) 


•H 


4-1 


CO 


c 


T3 


U-l 


o 


c 




CO 


bo 


3 


U-l 


"O 


4-1 


CJ 


QJ 




CO 


rH 






c 






1-1 




CO 


TJ 


U-l 


I-i 


CU 


cu 


cu 




t 


a. 




co 


CU 


o 


c 


ID 


4J 


T-l 


0.1 


•l-l 


03 


cr 


o 


c 




3 


Li 


4J 




3 






•r* 


"0 


U-l 


•V 


o 




V 


cu 




l-l 


u 


X 


cu 


o 


TJ 


L. 


C 




CO 


•H 


c 




CO 


Li 


E 


OJ 




o 


o 


TJ 


Q 


QJ 


QJ 


CO 






p- 


0) 


o 




x 


bO 


= 




>, 


CU 


CJ 


4-1 


Li 


o 




QJ 


4J 


CU 


bO 




T3 


•H 


bo 


3 




cO 


D 


>^ 


CJ 


4J 


o 


i 


OJ 


r^ 


CU 






co ui 


o 


co 


3 


c 


o 


bO i- 


> 


tfl 




CO 


c 


bO 


U 


cn 


> 


c 


TD 






C 


cfl 


O 


TJ 




4-> 






Li 




U-l 


CO 


Li 






OJ cu 


u 


xi 




1-1 


T3 


C 


4J 


CU 




cu 




o 


C 


CU 




i-4 


■H 


O 


CO 


CO 


•H 


O 


4-1 




E 


•H 


o 


QJ 


o. 


CO 




4-J 








a 


-o 






a) 


H 


C 


i-l 


c 


CO 


OJ 


> 


T. 


CJ 


i-l 


-C 


U-l 


4-1 


TJ 


X 


•H 


rH 


4-> 






0) 


CO 


rH 


•H 


CO 




4-J 


T3 




a) 








c 





>. 


c 


CO 


CO 


i— l 


CO 




> 


o 


4J 


CU 


i-l 


c 


O 


CJ 


c 


u 




CO 


rH 


>, 


CO 


CJ 


4-1 


•H 


bO 


O 


4-J 


rH 


OJ 


>> 


L 






cu < 


X 


— 


■H 


CU 


X 


CO 


CJ 


CO 


CO 


X 


c 


c 


CO 


cu 


o 


cu 


QJ 


OJ 


4-1 


OJ 


3 


tO 


H 


CO 


CD 


X 


O 


rH 


o 


3 


i-l 


CO 


o 






X 


S_l 


4-1 


S 


s 


CO 


cO 


cu 


i-l 


T-l 


X 


to 


CO 


fl 


OJ 


M 


M 


14-1 


Cl 


E 


H 


CO 


CO 


E 


QJ 


U-l 


>^ 


cO 


rH 


CJ 


c 


CO 


TJ 


T. 


CW 






c— 














CO 














c/> 
























C/J 




































X 
















1 
























, 


T3 




















1 












bO 














bO^- 






















1 


•H 


C 




















l-l 












3 














c 


1-1 






















C 


4J 


3 




















2 


u 










O 














•H 


U-l 






















o 


r-l 


O 




















CO 


o 










Li 














a 


C 


• 




















o 


3 


Li 


















a 


1 


•»», 










X! 














CO 


•H 


CO 
























bO 


















a 


e 


T5 










4J 














CJ 




00 




















T3 


T3 




















c 


o 


c 
























CD 


T3 


c 




















c 


c 


CU 


















v 


u 


CO 










c 


bO 












cu 


C 


•H 




















CO 


CO 


X 


















u-l 




• 








o 


C 














CO 


^ 
























4-) 






















co 


DO 








1-1 


•H 












E 




S^ 




















CO 


4J 




















c 


CO 


a 


u 








4-) 


CJ 












o 


0) 


o 




















Ll 


c 


U-l 


















u 


0) 


o 

Li 


U-l 








CO 
I-l 


3 












u 

U-l 


■a 


3 




















(U 

U-l 


i 


o 


















3 


o 


3 


i-l 








4-1 


cu 














cu 




















i-l 


OJ 


a) 


















c 


x 


O 


3 








— 1 


i-i 


• 










Li 




> 




















3 


> 


bO 


















— 


cu 


CO 


— 








•^ 




>. 










CU 


73 


i-i 




















cr 


o 


Li 


















u- 


u 




CO 








U-l 


>•. 


4-) 










4-1 


CU 


4J 




















cO 


s 


CO 


















c 


o 


h 










c 


Xi 


•H 










CO 


C 


o 
























X 


















•r- 


X 


0) 

4-1 


bO 

C 








1-1 


i—i 


i— 1 

•H 










3 


O 


tO 




















CO 
4-> 


QJ 
X 


o 

CD 


















CO J 


~ 


•H 








CO 


i-i 


X 










CO 


c 


bO 




















a, 


4-1 


•H 


















li 


bO 


3 


S^ 








4-1 


o 


to 










4-1 


re 


c 




















CU 




TJ 


* 
















c 


a 




-J 








c 


CD 


cu 










C 


X 


1-1 




















o 


CO 




Li 
















-. 


o 


cu 


l-i 








a> 




1 










cu 


CO 


^) 




















u 


rH 


OJ 


QJ 
















5> 


Li 


o 


a 








> 


CU 


l-l 










> 




tO 




















cu 


O 


4-> 


4-J 
















1 


x 


-. 


> 








<u 


X 


cu 










cu 


C 


Li 




















4-1 


L 


CO 


CO 
















L 


4-1 


U-l 


o 








M 


4J 


a. 










u 


CO 


4J 




















c 


4-1 


E 


3 






























Q 














Pm 
























M 
























3 








































































c 














^ 






































bO 






















1- 














i-t 






































a 






















r- 














O 






































•H 






















a 


1 












CD 














g, 
























M 
CU 






















at 


1 












CU 
CJ 


• 












r-l 
























4J 

CO 






















a 


1 












CO 


bO 












CO 
























3 






















— 


1 












U-l 


c 












cu 
























OJ 






















c 














U 


•^ 












0) 
























X) 






















X 














3 


r-l 


























































a 


i 












w 


- 












cu 
























rH 






















i. 


i 












X 


CU 












c 
























rH 






















r 


l 












3 


CD 












£ 
























<U 






















pc 


1 












C/J 




































3 























36 



TABLE 5. - Summary of water control costs 



Water control practice 



Cost item 



Cost 



Per 



Surface water controls: 
Runoff diversion.... 



Surface regrading and 
restoring. 



Soil sealing, 



Stream channel 
modification. 



Construction of diver- 
sion ditch. 
Construction of dikes.. 

Dumped rock 

Riprap 

Clearing and grubbing. . 

Backfilling: 

Contour 

Terrace. 

Revegetation 

Regrading: 

Contour 

Terrace 

Concrete 

Clay 

Rubber 

Asphalt 

Channel excavating 

Clay-lining bottom 

Channel reconstruction. 



$0.70- 

2.30- 

.55- 

.75- 

3.50- 

4.60- 

17.70- 

23.00- 



700 
1,740 

2,540 
6,260 
2,115 
5,220 
42.30- 
55.00- 
2.80- 
3.70- 
.70- 
7.60- 
.30- 
2.80- 
1.40- 
1.85- 
1.40- 
1.70- 
14.00- 
46.25- 



$2.80 

9.25 

1.15 

1.50 

10.60 

13.80 

44.25 

60.20 

700 

1,740 

2,820 
6,950 
2,540 
6,260 
775 
1,910 

5,350 

13,220 

4,790 

11,830 

84.60 

110.00 

8.50 

11.00 

1.40 

15.15 

.80 

8.50 

4.20 

5.50 

2.80 

5.10 

35.25 

115.60 



Linear foot. 
Linear meter. 
Cubic yard. 
Cubic meter. 
Cubic yard. 
Cubic meter. 
Cubic yard. 
Cubic meter. 
Acre. 
Hectare. 

Acre. 

Hectare. 

Acre. 

Hectare. 

Acre. 

Hectare. 

Acre. 
Hectare. 
Acre. 
Hectare. 
Cubic yard. 
Cubic meter. 
Cubic yard. 
Cubic meter. 
Square foot. 
Square meter. 
Square foot. 
Square meter. 
Cubic yard. 
Cubic meter. 
Square yard. 
Square meter. 
Linear foot. 
Linear meter. 



TABLE 5. - Summary of water control costs — Continued 



37 



Water control practice 


Cost item 


Cost 


Per 


Ground water controls: 










Grouting and grouting 




$50 


$113 


Linear foot. 


curtains. 




160.30- 


370 


Linear meter. 




Horizontal curtains.... 


16,900 


28,200 


Acre. 






41,750 


69,600 


Hectare. 






14 


28 


Linear foot. 






47 


93 


Linear meter. 




Sealing with cement 


21 


28 


Linear foot. 




grout. 


69 


93 


Linear meter. 


Subsurface soil 




2.80- 
9.25- 


4.30 
13.90 


Linear foot. 


sealing. 




Linear meter. 






2.80- 


6.35 


Bag. 






2.80- 


5.60 


Pound. 






6.20- 


12.40 


Kilogram. 




Fly ash 


11.30- 
12.40- 


28.20 
31.00 


Ton. 






Metric ton. 




Horizontal grout 


16,900 


56,360 


Acre. 




curtain. 


41,750 


L39,160 . 


Hectare. 




Dry seals: 

Masonry block seal... 










3,520 


4,230 


Seal. 






2.80- 


5.60 


Cubic yard. 
Cubic meter. 






3.70- 


7.40 






3,520 


6,340 


Seal. 




Hydraulic seals, double 










bulkhead: 










Grouted aggregate. . . . 


14,100 


42,270 


Do. 






21,150 


25,360 


Do. 




Seal and curtain 




28,180 


Do. 




grouting. 










Hydraulic seals, single 


7,050 


14,100 


Do. 




bulkhead. 










Curtain grouting: 










Vertical curtains.... 


49 - 


113 


Linear foot. 






160 


370 


Linear meter. 




Horizontal curtains.. 


16,900 


28,200 


Acre. 






41,750 


69,600 


Hectare. 








36,970 


Year, per 
million gpd. 










19,460 


Do. 








13,430 


Do. 



38 



technical and economic performance of a 
dewatering system in Appalachia. Conse- 
quently, a very heavy emphasis has been 
placed on the results of case study 1. 

Case study 2 was a preliminary feasi- 
bility study conducted by a private min- 
ing company to evaluate the advantages 
and disadvantages of dewatering a new 
mine in advance of mining. Both techni- 
cal and legal factors were considered in 
this study; however, the major considera- 
tion was whether the additional costs in- 
curred by the dewatering system would be 
recovered through a reduction in unit 
production costs. It was concluded that 
legal factors alone made the project un- 
feasible. In addition, the complexities 
of the technical problems resulted in 
both a technical approach and related 
high costs that made the project prohibi- 
tive to implement. 

Case study 3 involved an ongoing at- 
tempt by a mining company to control wa- 
ter inflow in the last working section of 
an old mine. This situation occurs with 
some frequency in Appalachia and often 
results in substantial amounts of coal 
left unmined because of difficult mining 
conditions. The approach being attempted 
consists of inducing subsidence in the 
area of heaviest inflow to concentrate 
the mine drainage in a system of sumps, 
which will then allow the safe extraction 
of the remaining coal. This demonstra- 
tion will not be completed in time to in- 
clude a discussion of the actual effec- 
tiveness in this report. This method 
does, however, appear to represent a 
practical approach to the problem, and it 
provides an interesting comparison with 
the other two case studies. 

The geologic conditions of the three 
study sites are compared and summarized 
in table 6. The parameters compared are 
(1) the coal seam mined, including depth 
and thickness, (2) the mining method 
used, (3) the surface geology, (4) the 
subsurface geology, and (5) the major 
structural features. 

The hydrologic conditions of the three 
study sites are compared and summa- 
rized in table 7. The parameters com- 
pared are divided into three categories: 
surface water, ground water, and mine 



water. The surface water parameters 
include (1) drainage basin, (2) water- 
courses, and (3) springs. The ground wa- 
ter parameters include (1) aquifer(s) and 
(2) aquifer properties. The mine water 
parameters include (1) sources, (2) in- 
flow rate, and (3) method of control. 

TECHNICAL EFFECTIVENESS 

Case Study 1 

The technical effectiveness of case 
study 1 is described in detail in appen- 
dix A. As the data show, the dewatering 
operation had little impact on controll- 
ing the quantity of water flowing into 
the mine; only a 34-pct decrease in mine 
inflow was realized. The following de- 
scription of the area's ground water con- 
ditions offers an explanation as to why 
the dewatering operation was ineffective. 

The inflow rate at the test site was 
estimated to range from 100 to 150 gpm 
(6.3 to 9.5 L/s), yet the geologic and 
ground water conditions of the area indi- 
cate that aside from the Saltsburg Sand- 
stone, no discernable aquifer units ex- 
ist. In addition, a rapid response to 
heavy rainfall was observed in the well 
water levels and in the mine inflow. 
This indicates that the ground water sys- 
tem is fracture controlled. Since most 
of the water is located in the fracture 
zones, wells that do not intersect any of 
these water conduits will do little to 
relieve the water problem in the mine. 
The study demonstrated this very well. 
The wells could only intercept some of 
the ground water storage space, while the 
major avenue of water infiltration into 
the mine was never dealt with. As a re- 
sult, only a small decrease in the mine 
inflow was achieved. It must still be 
demonstrated technically that dewatering 
in advance of mining can be achieved when 
the ground water conditions are fracture 
controlled. The fractures must be well 
delineated and their hydraulic character- 
istics well defined, so that wells can be 
properly located. This is not beyond the 
technology available today. Parizek and 
Tarr (25) have demonstrated that water 
supply wells sometimes can be located via 



39 



tj 

3 



QJ 
CO 
CO 
CJ 

41 
01 

u 

X 



tj 
c 
o 
u 



bC 
O 

— 

o 

- 

bC 



c 
o 

CO 

•M 
u 
CO 
a. 
e 
o 
u 



j 

09 

< 













1 














^ 


1 






.. 




1-1 










0) CD 










c 






* 


1 






1 — 


4J 




>< 


l-i 


-a 1 


cu 










^ CO CD 










o 




4-1 


>sXl 




1 


J4 


i— 1 




I— 1 


1 OJ 


C 0) 


X 






OJ 




•M 0) 










o 




c 


to 


o 




- 


O 


■H 




4-1 


CO X 


CO t-i 1 


E 


• 




rH 




1-1 0) rH 










c 




OJ 


l-l 


CJ 




e 


iH 


CO 




CO 


6 e 


O- T3 


OJ 


1—1 




rH • 




4J > 










3 




•H 


CJ 






i-i 


X 









l-i 01 


0) 1 3 


£ 


CO 




-M 01 


ft 


CD CO CM 










1 




o 




TJ 




o 


4J 


* 




f 


s 


C T3 CO 




O 




> 3 


3 CD 


X 










1 TJ 




3 


T3 


c 




Pb 




CO 




Pu 


O •• 3 CO 


X 


CJ 




CD iH 


OJ Jj! 


CD 










0! C 




CO 


01 


cfl 






O 


01 




1 


l-l 


4-1 CD 6 









C <-A 


O. 3 


0) CD 0) 










r-l 10 






4-1 






e 


4-1 


l-l 




l-l 


3 0) 


CD l-i TD 


CO 


CM 




3 CJ 


O CO 


X TJ bo 

< rH C 










OJ 






CO 


* 




3 




CO 


• 


01 


3 — 


TJ 0) -O 3 


01 


O 




O 3 


rH 


r— 








c - 






c 


CO 


• 


o 


>^ X 


CO 


s: 


O O. 


01 X 01 CO 








rl 5^ 


- C4H 


O 3 










C 13 




3 


i 


OJ 


CO 


4^ 


1— 1 


CO 


OJ 


E 


4J 33 


a; e tj 


U-J 


M 




P9 CO 


rH 


CM <-l 


>v 








to C 




O 


1— 1 


l-l 


c 


3 




3 


0) 


3 1 


0) TJ « 


O 


01 






CO ^ 


• 3. 


TJ 








x to 




•H 


CO 


x> 


i 


o 


i-l 


» 


O 


X 


O 1 


- X! 01 co 




>~. 




4-1 


O U 


co X 


a 








O CO 




4J 


l-l 


£ 


— 


•H 


X 


00 


(J 




-H X 


4-1 X 0) 


0) 


CO 




• • l-l 


•H O 


CD 4-1 TJ 


— 












i 


1 


V 


■-4 


c 


4J 


01 


CO 


u 


C bO 


O X l-i 3 


CO 


r-l 




CD 0) 


l-l 4-1 


01 O l-i 


■ 








p « 




1 


o. 


3 


= 




3 


t: 


01 


33 1-1 


a. bo 01 


cfl 






TJ-X 


4-1 CO 


rH CO CO 










01 4-1 




u 


IB 




o 




>-. 





a 


Q. 


3 


• X l-l 4J 4-1 


X 


CO 




rH S 


0) •-< 


3 


i 








> -< 




o 


i-t 


» 


x> 


T3 


1— 1 


4-1 


e 


C- 


-O X 


0) CO 3 3 CD 








O CO 
CM fJ 


E 3 


u X 


a 








iH -H 




'— 


01 


00 




C 


4-1 


en 




35 


3 CO 


> i-l X iH 4-1 


01 


>N 




E T3 


• 4-1 


- 








l-i CO 






3 


T) 


01 


CO 


CO 


TT 


TJ 


1 


CO 4-1 


O fa-, CD rH 


£ 


X 






S 3 


fa! 3 


•_: 


• 










CO 


C 


c 


E 




O 


C 


3 


1 


• 4J 


X 4-1 f^ i-l 






rH - 


co 3 


O 




x 




CD 13 




1— 1 


CO 


CO 


o 


t>0 


e 


Cfl 


CO 


X 


01 bC 1-1 


tt) » 4-1 1— 1 CO 




TJ 




CO 0) 




CO CD 




t>C 




3 •• OJ 


• 


i 


^: 


CO 


en 


l-i 




CO 




be 


3 U P- 


>^ i-l 4-1 




OJ 




3 3 


0) 01 


in . 




h 




o e -u 


CO 


CO 


U 






3 






•» 


1-1 


O 3 


CO 0) 0- 3 - 


• 


X. 




iH -H 


M > 


M-* rl O 




3 




3 3 W 


OJ 


SI 




» 




X 




X) 


cc 


3 


4-1 X - 


CO i-l CO CD 


CO 


u 




rH i-H 


CO CO 


3 1 Cfl rH 




x 




C i-i T3 


1— 1 


CJ 


t-i 


00 


• 


a 


to 


01 


0) 


X 


CO CD CO 


J* U 3 0) 


QJ 


cfl 




O O 


X 


■Ho t-i 




co 






1 > —1 


X 


•^ 


01 


4J 


00 


0) 


c 


T) 


3 


CO 


01 01 3 


01 O 0) i-l 3 

e -h 3 e 


3 


E 




3 -H 


X 


CX in 0) 3 




u 




4-1 3 i-J 


X 


§ 


> 


•H 


01 


3 





T) 


O 


4-1 


B 3 O 


O 






>> 4J 


4-1 TJ 


3.01 3 co 




4-1 o 


C -J O 


o 


u 


1-1 


i-l 


^ 


X -w 


01 


4- 1 


4J 


1-1 >-. T-1 


to 3 O O 4-1 


4-1 


CD 




CD 3 


O 3 


•H 0) X 




■H O 


' O M CD 


u 


r. 


l-l 


CO 


Xi 


cfl 


4J 


X 


CO 


•H 


r-4. CO *-> 


CO 01 i-J TJ CD 


CO 


1-1 




cfl 


PQ CO 


TJ Z bO 4-1 




B.-»0OU< 




CJ) 








s 








P- 


5 


00 








CN 


















1 

3 




1 










































1 * 3 


CO 




iH 


















4-1 1 


•* 






















• • 3 


CO 


1 


^-1 
















• 


l-i bO 


>, 








1 


■1 












■ • O 




iH 


■H 


• 














01 


O 3 


cfl 






TJ •• 


^-1 


fal 












> • l-i 


ft 


CO 


CO 


>s 














> 


a. 01 1-1 


r-t 






3 CD 


0) 














■ • X 


0) 


CJ 


00 

o 


cfl 

— 














O 
X 


0) CO <4-l TJ 


u 






cu a 

U -H 


l-i 




\£3 












• -o 


o 


01 


M-l 


CJ 














CO 


l-i X 33 3 


OJ 






4J TJ 


• * 


CN! 












> • c 


4J 


6 




















fa- CD 1 CO 


t-i 








rH 














• • cfl 


CO 


O 


01 


01 














CO 


1 


1-1 






■ #s 


CO 


• z 


CM 












4-1 


CO 


1 


t-l 














CO 


l-l •* 14-| B 


fa 






•• 4J 


O • 


CO 












■ • >srH 




o 


1-1 
















01 4-1 O l-l 








OJ CD 


O ,3 


4-1 « 


>■ 










• • CO 


•H 


• 


CO 


«-| 














0) 


O. CM O 1-1 


1-1 






3 0) 


■H 


rH fal 


— 










• • u 


CO 


as 


















s 


a. m >m 


CO 






iH 3 


CM CD 


3 


- 










• • sc 




■o 


•* 


OJ 














CO 


33 CD 


> 






rH X 


O co 


cfl 


— 












ft 


01 


01 


E 














CO 


•^■H 






CJ 4J 


X 


cm r-~ • 


:- 












- 
— 


-C 

— 


C 

o 


o 

CO 














,. 


>-. cu 1— 1 

•• r-l i-l 4-1 


i-H 
O 


. 




3 3 


O 3 


3 
z • 


'. 










> • a. 


CO 


01 


4-1 
















a 


O. 0) TJ CO 


CQ 


4-1 




CO CO 


S-l -H 


•H fal 


•-: 


u 






• • 3 


x 


1-1 


CO 


» 














3 


3 > tj g 


1 


CM 









bO —1 


- 


1-1 






> CO 


CO 




>» 


CO 














O 


O 1-1 -H E 

M 4-1 E 


1 


O 




CJ 


4-1 4J 


O •• — H O 


~ 


o 






' a. u 




OJ 


cfl 


01 














l-i 


t-l 


CD 




CO 4J 


3 CO 


rH CD CO 




EV 






3 a 


ft 


E 


— 


l-l 














O 


to 


O 






E 


^ 


O T3 Z -d" 




4) 










01 


o 


o 


cfl 
















■-I 3 0) 


O 


t^ 




O 4J 


CM 


01 3 




oj 






i- x 


c 


CO 




-= 














X 


^ 1) Tl H 


r-l 


r-l 




4J CO 


M 


bO 0) - Z 




u 




C 


bC 60 


o 




CO 


0) 














M 


3 m cfl 


Uj 


r-t 




O co 


CO >. 


l-i fal 




fa 


c 


r. 


3 


4-1 


•» 


3 
















3 


CU MX 




CO 




a< 01 


OJ rH 


01 4-1 








c 


— i eg 


CO 


0) 


o 


0) 














1 


X •• 0) CO 


• •* 


O 




X 


3 OJ 


3 c... 




1-1 




**- 


-J E 


>, 


- 


01 


3 














bO --I TJ 


T3 


•H 




X 4-1 


> 


t-i l-i -0- l-i 




01 — 


c 


4- 


O 01 


CO 


o 


u 


o 














0) 


OJ cfl 3 3 


t-l 


CD 




4-1 t-l 


iH 


4-1 r~- 




c c 


4- 


C 


CO 3 


l-l 


4J 


cfl 


t-l 














3 


i-H O -H O 


CO 


CO 




t-l 


00 4J 


•r-l 3 




a. c 




c 


> O 


CJ 


0) 


CJ 


0) 














O 


,H O X 4J 


X 


X 




O 3 


r* to 


O co Z -H 




33 IT 


ac 


c. 


sO CJ 






















c_> 


< 








2 




Z !2 S 












T3 






>» 
























1 

T3 T3 




M 














C 






X 






C 










3 


1 1 






3 3 




01 














to 




0) 


T3 






O 


0) 

c 








O 

T-l 


0) Ij 

01 a) 


1 

T3 


T3 


CO co 4-1 
co cfl 


# 


X 

4J 














s^ - 




CO 


OJ 






4-1 











4J 


M 4-1 


C 


3 


r-l 


X 4-1 

















h e 






U 






« 


4-1 








CO 


fa. 3 


cfl 


CO 


M co co 


4J CD 


3 














4-> 3 




01 


0) 






e 


CO 








g 


CO i-l 


co 




CJ S 


•s s 


CO 














0) T-l 




f— 1 


> 






ti 


— 








p 


.« c 




01 


•H CJ CO 
















> 




<0 


o 









3 








O 


0. >, 


* 


3 


X 0) 


X 


OJ 














1 3 




si 


o 






■— 


cfl 








[r, 


3 1-1 1-1 


CD 


O 


4-1 CO CO 


bO 4J 


3 














— - 




CO 










CO 










O 4-1 4-1 


01 


4-1 




3 3 

















r- 






►. 






3 










3 


l-l CO CO 


c 


CD 


CN bO rH 


•H O 






— 










. .. o 




T3 


v— 1 






CO 


T3 








cfl 


bo E O 


c 


01 


3 CO 


>> CO 

















• CO o 




3 


i-l 






X 


OJ 








X 


M S 


4-1 


B 


•H O 


rH | 


4-1 




> 










t— i 




CO 


3 






CO 


X) 








CO 


4-1 


CO 


•H 


.. X U 


4-1 






— 










. CO « 






M 






e 


— 








3 


CD fa. 


U 


r-l 


3 O 


4-1 CD 


r-l 




r 










■h e 




OJ 


01 






OJ 


OJ 








OJ 


01 


iH 




O 1-1 


co CO 


0) 




— 


r> 






t- 3 




3 


3 






— 1 


X 








^ 


TJ bO 3 


•H 


QJ 


•h 3 . 


<-t 01 


rH 




-.- 


CO < 






OJ — i 
■u > 




O 

4-1 


0) 
00 









Ss 











r-l 3 O 

O 1-1 1-1 


CO 


B 



4-1 TJ 4-1 

CO 3 -H 


>M 

• OJ 


rH 

cfl • 




- 








T, 3 




CO 










l-l 










3 4-1 


» 


CD 


E CO 3 


E >%X 


M CD 




•-'. 


sc 






1 -^ 


• 


•o 


* 








M 








• • 


"3 co 


CO 




l-i CO 3 


O rH 4-1 


CO OJ 




- 


3 






rH 


r -i 


c 


3 






a. 











a. • 


a to B 


QJ 


X 


O 


4-1 ^ 


O. M 




- 


— 






T3 to 


iH 


CO 


01 






3 


tA 








3 01 


3 4J •• M 


r-l 


4J 


Cxi CO 01 


4-1 tfl O 


X 3 






■z 






> 4) 


o 


CO 


14-1 









X 








> 


O 4J 01 O 


CO 


•H 


4-1 r-l 


O l-l 4-1 


3 4-1 






■z 






4-1 >S 


CO 










M 


4-1 








i-i 


M iH M fa. 


X 


3 


bO 1-1 CO 


x 01 


CD CO 






s 






i CO U 




U-l 


>, 











• 






X 


O U OJ 


co 




a c j= 


3 a. 


01 






4-1 C 






-O CO 


>, 


O 


— 








O 


01 






CO 


X 4-1 




* 


i-l 3 CO 


TJ QJ -H 


01 <M 






4J 1/" 


i 




► •-- C. 


u 




01 


• 




X 


4-1 


I— I 






X 


>M3 M 


TJ 


CD 


3 


3 bO TJ 


M 






2- 


i 




— ' u 


CO 


CO 


> 


-H 




-~ 




cfl 






bO co 


3 3 4J O 


'■J 


01 • 


3 OJ ^ 


cfl 


CO U 








► r- 


O 0) 


4-1 


o. 


— H 


1-1 




3 


>, X 






3 cfl 


01 CO 3 O. TJ 


3 rH 


CO 3 CJ 


CD OJ 


rH 






c 




- 


CO 4-1 


c 


o 


4-1 


o 




- 


t— 1 


CO 






Cfl 


X 01 01 


T3 


O cfl 


4J O 1-1 


D. iH rH 


CO 3 






U 4. 




1 


3 U 


01 


t-l 


CO 


<0 




E 


3 








S 01 


bO 4-1 co 0) 


0) 


4-1 O 


4J 4-1 X 


O 4J 


4-1 CO 






OJ 




C eo 


•c 


o 


l-l 






'j 


•H 


■3 






01 B 


01 M 01 M 


-0 


CO 


iH CO 4-1 


4-1 CO 3 


CO «H 






3 C 






CJ 3 


01 


4J 


01 


>> 




C 


c 


3 






3 CO 


r-l O M fai 






u 


0) 0) 


M 






3 5 


>/■ 


r- 


3 O" 

33 


0) 


9 
o 


l-l 


Xi 




O 

'-J 


4-1 


CO 






O CO 

c_> 


2 0- a 








_M M 


4-> O 
C/3 Z 




































• 
• 


























> ^ 






















bo 
O 










rH 

CO 






- 










• V. 






















O 










P 






-- 








► T. 


1 O 






















0) 










3 






— 










— 






















H 










4-1 






-- 






> a 


X 


o 
































CJ 






E 


• • 




7 


- 


I OJ 






















0) 










3 • 






r 


S 




> 4 


'. 


V. 

































IJ CO 






- 


a 






E 
























cfl 










4J 01 






r 


o 




_< 




4) 






















14-1 










co l-i 






- 


r V — 
— ' Jk C 

- h e 
o 


c. 


a 


C CJ 

: a 

1 CM 

- 






















1- 
3 

go 

X 

3 










3 
1-1 4-1 
O CO 
1-1 0) 

tfl CM 








u 






X 


C/3 






















C/3 










£ 







40 



Xl 

3 



3 
co 
3 
o 

cu 
3 

S-i 

43 



X) 

3 

o 
o 



bO 

o 

i-l 

o 

l-l 

4-i 
O 

(3 
O 
CO 
•H 
U 
3 

o 

C_> 












* 












• • 


















M 















X) 




• 


4-> 






3 












a a 


CU 







x» a 






3 








1 




bO to 


4-) 




a 


3 cu cu 






u 








CO 






4- 






• bO 


3 4J 3 CJ 






o 








4-> 




u-i -3- 


i- 






XJ 


3 3 u 








u 








4-1 




\D ro 






a • 


CD CU 3 






t^ c 








•H 






c/ 


• 




bO 


CX CU 14 bOil 






XJ 3 






1 


p.. 




• • •• 


c 


CD 




ro a 


> O C C 






Xl 4J 




CD 






3 3 


3 3 




3 bO 


3 3 -H i-l 




m 


.2 w 




bO 


* 




3 3 


l- 


3 







CX43 3 






E -H 




3 


CU 




O O 


4-1 3 




•H 4-1 


• 4-1 -H O 




^ 









•H 


3 




4-> 4J 


1 


iH 




■H m 


X) bO 3 4-i 




id 


• 


► 1-1 




l-l 


o 




CD CO 


1 


P. 




iH O 


3 3 > bO 1 




3 


5-J J— i <3J 




CX 


4-1 • 




X) X3 


l- 






■gg.. 


3 i-l i-l C -O 3 




4-J 


CU CU 4-> 




CO 


CD CU 




3 3 


3 bO 




3 4J 1-1 3 3 




co 


P> > c 








•3 3 




3 3 


> 3 




CO 


ffl -H O 3 OH 
CX 3 3 O 






•r-j -r 


1 "H 




■H 


3 O 




CO CO 


(5 


•H 




CN CU 




0) 


c2 on 




r-l 


CO 4-1 






X3 




•• i-l 


14-1 3 CU 




CO 




<+4 








w co 




b0 43 




XI 




3 O 


3 r-l M-l i-4 CO CU 




<fl 


CO co ( 








X! 




l-i bO 


3 <n 




•• 3 43 


CO 3 3 CX X\ 


• 


U 


1-1 1-1 




CO 


bO 3 




3 l-i 


i— 


43 




3 l-i 


C C >. 4J 


u 




cu cu s-j 


• 






l-i cO 




43 3 


cu 




3 3 4J 


<4-l O l-l >, 43 


3 




x. 4= 


CU 


CO 


CO 


3 CO 




CD 43 


4: 


43 




i MO 


O i-l i-l U-l 


4-1 




3 3 43 





3 


4a 




CU CD 


3 bO 




4J XI 4J CX O 


3 




DO bO 


CO 


o 


CO 43 


• • 


3 4J 


bO 3 




3 4a 


CD O 3 3 


3: 




3 3 3 


CU 


t-l 


CU bO 


X) 


>» 4-> 


c 


O 




CU -H 


CU CU > CU 3 3 






O O 3 


1-J 


cu 


3 1-J 


l-l 


3 -H 


l-l 




.-I 4«i <4-l 


•H l-l O M CD 3 


<U 




(3 C 




4-> 





^ 3 


cu 


3 P-i 


c 


43 




l-l 


14-H 14 n l-l 


43 




O O CO 


CO 


3 


cO 4a 


•H 




O 4J 




,3 


CU X) CX 3 3 3 


4-1 




£ 2 


1 




5s 


D£ 


>- 




£ 






$ & Pi 


CO 








-3 


• 








• 






















3 


CO 






4-> 


CM 












CD 








. x: ■" 









CD 


4J 












3 


• 






• 4-> 


cO 






O bO 


<4-l 












1 i-l 3 


3 






• l-l - 


cu 






3 


— ^ 












CU l-l 3 U-l 


O 3 






. O W 


1-1 






•H 


-3 




3 






3 l-i 3 43 O 3 


U 3 






' Z CD 


4-) 






3 


a 




3 




• • 


•H CD 3 43 


U-4 14-1 








> 


CO 


a 


i 


.. O 


bO 




O 




4J • • 


• 4-> CU 


l-i 






1 






4. 


i 


CO 43 






4-1 




3 x) x> 


Xl bO 3 <U CD iH 


CD 3 


CN 




« 3 PS 


u 


1- 


I 


til 


r^ 




CD 




3 cx a 


CX 3 43 CD • 3 1— 1 


■H CD 




3 : 


cu 





1 


-tf 




X) 




bO bO 


bO i-l 3 CD 43 -H 


i-H 


>> 


iHOJ O 


i-H 


1 




3 


o 




3 




CX 


14 bo cx 5 


CU (1) 


-o 


co 


cO 


i-H 


c 




3 l-i 


• 




3 




000 


O 3 3 i-H 43 


3= X 


3 


CO -H 


crt 


c 




<U 


o 


• 


CO 




i-H O O 


O 4J 1-4 i-H 3 CJ l-l 


4-1 


4-1 


pa cu o 









l-i 13 













mmo 


m CO 3 i-l CD 3 3 


43 


CO 


l-l 4J 


CO 


b 


p 


CU O 




& 


bO 




^ #v #* 


- 3: -h 12 a) 4-j 

CU X) l-i CO 


bO O 




CJ 3 O 




c 




44 kJ 


• • 


bO 


3 




CU O H 


3 4-1 


CU 


3 3 CX 


<4-l 


'1- 




•H 1 


>■> 




•H 




XI ^H CN 


— 1 xl 3 & 


O 


CO 


hJ 


o 


V 


i 


3 1 


• 4-1 


CO 


3 






14-4 • 3 CO 


l-i CD 


CO 


o 


<4-l 




c 


u 


a" 4-t 


CU -H 


1 


O 




l-l 


X) O 4J C - 


43 CX 


CJ 


4J 


► o 


S-i 


c/ 


i 


CO 3 


3 .H 


CN 


43 








4J 




O (3 


cu 






3 


O i-l 




cc 






<! PQ 


U l-i 3 CX -r-l 3 


5 




CX 3 43 


43 


c 




VJ 4J 


4-> 43 




S 




1— 1 


3 O Xl 4J iH 


Xl CD 




Pi O 





3 




O l-i 


CO CO 


• • 








3 3 


3 x) 3 CU 3 3 H 


3 




W 


3 


3 


c 


I 


•r-> O 


-3 CU 


XI 


l-i 




l-i3 3 


C i-l 3 4J a li 


a c 




3 X) 3 


3 


c 




CO CX 


3 


i-l 


3 




3 -H -H 


•H CD > CJ cu 3 


-H 




CX 3 l-i 




^ 







CO l-i 


3 


s 




W S g 


S 3 X3 3 4-1 CX £», 


3 3 




&, co pa 


to 






•H 


CO cu 


•H 







"H 


O 3 T-) O O CD 


CX 




1=) CO 




"~ 


i 


r~- 


fu 


tH 


kJ 




<H 


O 






• 


i 








/~N 










3 


• 


1 CD 








• 4* 








co 


•3 










l-i 


XI • 


3 3 








' <u 






S 


CU 


o 








3 


CX 


1-133: CM l-l 
3 








. CU 






o 


X 


o 








4-) 


bO & 








> l- 








1-1 


o 


ro 




bO 


O 


bO 


•H S 4-1 








> c 


> 




4- 


M-4 

1 


u 
cu 


O 




3 1 
•H 1 


3 
U 


3 
O O 


U-l * O CD 3 
O 3 .-I 3 3= 








> 4-> 




•1- 


43 


ex 


4-1 




>% co 


M-4 


•h m 


U-l i-l CU 








• CO 




3 


u 


s— ' 






r-l 4li 




iH -H 


3 3 l-i XI 




.—1 




• CU 






•H 




O 




l-l 


43 


l-l 


3 4-1 i-H CU 








' X 






(J 


3= 


CU 


o 




3 O 


bO 


IS 


C ^ CD O 




>^ 




• c_ 






b 





3 


CN 




> l-l 


3 


CO 43 CU 4J 




-o 


U 






c 


co 


o 









O 




> 3 3 




3 


<u 






•f- 


• CX 


■u 








bO 


l-i 


• -* 


X) « -H CO 

3 Xl bO a 




4-> 


> c 






s- 


CU 


CD 


• • 


• 


3 t 


43 


• CD • O 




CO 


(2 p£ 






c 


u ex cu 


-3 


^ 





•t- 


•H 


4J 


IH 1) CO H 


3 3 










Cf 


bo co 


a 3 


4J 


a 




XJ 




O 3 


p! 4J 3 • -H 3 




CU 












bO 3 


•H 


bO 


M C 


XI 


2 * .. .. 


•H CD i-H 4-1 CO CX 




co 


CO 4* 






14- 


m 14-1 


CO 


> 




3 3 


3 


3 3 3 




CO 


(3 O 




c 


o 


CN! 


•H 


r~- 


4-> O 


4J 


CU 3 


bO 4J 3 CX x) 


• 


o 


3 -r 


1 






4-1 


bO 


CD 


CN 


3 l-i 


4-) 


3 XI 3 3 


3 O >s 3 


3 




cO ^ 






J. 


O l-i 


O l-i 


CO 


• 


3 


l-l 


•H 


•h 3 -h 1-1 

3 3 


•H (0 i4<frl 3 


3 




43 






a 


1 cu 


u> 3 


1 


4J 




3 





Ij U U ro u 


-0- 




CU i- 


1 




4= 


co 4a 


43 


<4-l •• 


XI CD 


CO 


CD O 


3 S cj 3 co 




3 a 


1 




£ 


S 


•-H CO 


co 


^. X) 


e 




3 


3 XI 3 >, 


4J 3 >^ 3 CX 






W i- 


I 






O 3 


4-1 


3 


X) iH 


3 X) 


3 


3 3 iH X) 


3 bOX) iH Ij 


3 




CD S 


1 




c 


H 3 


y-i iH 


3 


Ci 3 


O 3 


l-i 


O 3 O 3 


3: 3 3 3 l-i 3 


43 




3 ct 








4-1 


O 3 


l-i 


bO -H 


l- 


3 


4-> 


N 43 43 4-1 


3 -H l-i O 3 CO 


4-1 




co h-- 






< 


«u 


CO 


H 


>* 


e 


1 




<t) J5 CO 


O O 




















CO 


l-l 
•> O 












• 
• 
• 




















cu 


CO 












i-H 




















•H 


cu ~ 












O 




















4-» 


•H CD 












M 






3 












l-l 


4J CU 












4-1 




W 


•H < 












cu 


•H i-l 












3 




CU 


•• CO V 












a 


> 4-1 












O 




4-> 


u co a 










• « • 


o 


•H -rl 








3 


O 




0) 


cu 43 cr 










l-l ^-v 


M 


CO i-l 








4-> 









4-> l- 










CU CO 


O- 


CO l-l 


•• 1 






3 


1+4 




CO 


cO cu C 










4-> ^-^ 




•H 43 • 


u ■ 






M 


O 




S-i 


3 60C 






V 




3 l-i 


l-i 


3 co 


cu cr 












cO 


cO c 






h 


) 


S cu 


3 


CD CU T3 


4-1 a 






3= 


XI 




CU 


cu 3 i- 






(= 




<4-l 


14-1 


3 0^-1 


CO c 






O 









o -h a 






•,- 




T3 i-l 


•H 


3l-i3 


3= 1- 






i-l 


X 






CO CO 4- 






i- 




3 3 


3 


l-i 3 i-l 


^- 






4-1 


4-> 






<4-l l-l Ct 






c 


u 


3 cr 


cr 


4J CX >. 


3 c 






3 


3 






l-i Q 3 






co 




o < 


< 




3 co 






1-1 


a 






3 










u 






•H 














co 












o 






s 















41 



fracture analysis. However, the impact 
of this technology on mine water inflow 
has yet to be demonstrated. 

Case Study 2 

The technical effectiveness of case 
study 2 is described in detail in appen- 
dix B. In this case, dewatering in ad- 
vance of mining was considered primarily 
because of the high cost of tramming 
within the mine under wet conditions. 
Each mine in this area receives inflows 
of approximately 10,000 to 20,000 gpd 
(37,850 to 75,700 L/d) in the first year 
alone. This amount increases as more 
mine area is exposed. Dewatering in ad- 
vance of mining was also considered be- 
cause the region is artesian. Unfortu- 
nately, test wells drilled to evaluate 
aquifer characteristics showed that the 
sandstone unit above the coal seam was 
not permeable enough to pump, yield- 
ing only 2 to 3 gpm (0.13 to 0.19 L/s). 
These results indicated that dewatering 
in advance of mining would be difficult 
and expensive, owing to the number of 
wells necessary for effective dewatering 
and the cost of drilling these wells. 
Also, the mining cycle would advance too 
rapidly for dewatering to be effective. 

In addition, it was found that the nat- 
ural water in the area has a pH of 4.0 to 
4.5. State regulations require that wa- 
ter in this pH range be treated before 
being returned to the environment, which 
eliminates one of the major advantages of 
dewatering prior to mining. 

After considering these and other 
facts, it was decided that dewatering in 
advance of mining would be technically 
and economically impractical for this 
area. 

Case Study 3 

Water has caused significant problems 
in the operation of the Nemacolin Mine 
(fig. 6). The inflow of water into the 
working section of the mine was so great 
that it disrupted face operations even 
with an adequate dewatering system of 
pumps and sumps. To remedy this problem, 
the mine engineers decided to vary the 
direction of mining by 90° , advancing the 




FIGURE 6. - Map of Nemacolin Mine. 

operations away from the Monongahela 
River, which borders the mine, instead of 
paralleling it. This brought some ini- 
tial relief, but with time the problem 
returned. 

The mine engineers decided that the 
best way to prevent the disruption of 
face operations was to dewater the over- 
burden before the water reached the face 
operations. They are second-mining the 
area just north of the 90° turn and down- 
dip of the Monongahela River, thereby 
creating a huge sump where water will 
collect. This water can then be pumped 
out of the mine. 

This system is basically a modification 
of the gravity drainage and mine pump- 
ing system of dewatering the overburden 
above a mine (fig. 4). Instead of using 
drilled holes to collect water, the water 
is collected by fracturing the confining 
bed and part of the source bed so that 
the water will run along the fractures 
into the mine. 



It would seem that this type of over- 
burden dewatering system is very well 
suited for this kind of situation, since 
most of the water entering the workings 
is traveling along bedding planes from 
the Monongahela River. Although it has 
yet to be demonstrated that this type of 
system can adequately drain the overbur- 
den, the system is technically and eco- 
nomically feasible in this situation. As 
already stated, it would be necessary to 
second-mine an area of coal in order to 
implement this system. This would actu- 
ally generate more income, since the coal 
could then be put on the market. In ad- 
dition, no roof support would have to be 
instituted. The area would need less up- 
keep after retreat mining, resulting in a 
more economical, stable, and water-free 
environment. 

COSTS 



included well drilling and aquifer test- 
ing, they decided that this approach 
would not be cost effective for the fol- 
lowing reasons: 

• The aquifer unit feeding water to 
the mine is not permeable enough to pump. 
Maximum well yield is only 2 to 3 gpm 
(0.13 to 0.19 L/s). In order to dewa- 
ter the mine using wells, the wells 
would have to be placed on 100-ft (30-m) 
centers. 

• If the water table or hydrologic 
balance is altered, a potable water sup- 
ply must be made available by the mining 
company for the area's landowners. 

• The natural water in the area has a 
pH of 4.0 to 4.5, which is not potable. 
By law, this water must be treated before 
being returned to the environment. 



Case Study 1 

The cost effectiveness of this demon- 
stration project is detailed in appen- 
dix A. The overall conclusion of this 
specific project was that individually 
pumped wells constructed from the surface 
do not appear to be cost effective in 
controlling water quality at the specific 
demonstration site, unless the average 
well yield can be increased from the 30 
gpm (1.9 L/s) used in the analyses. On 
the average, the cost of well dewatering 
at this study site appeared to be at 
least twice that of present water removal 
and treatment methods. 

In addition to the requirements for 
higher flow rates as described above, two 
other factors were offered to improve the 
cost effectiveness of this approach: The 
acidity concentration of the mine water 
should be in the range of 500 to 1,500 
ppm (500 to 1,500 mg/L) , and the coal 
seam depth should be less than 150 ft (46 
m) . 

Case Study 2 

Mine engineers studied the possibil- 
ity of using individually pumped wells 
constructed from the surface to control 
water flowing into the mine. After a 
period of information gathering, which 



• The company would need to purchase 
surface rights for access, power lines, 
etc., needed for the wells. 

• The cost of drilling in hard and 
fractured rock is extremely high. 

Case Study 3 

No cost data are available for this 
situation since the mining company did 
not investigate the use of individually 
pumped wells constructed from the surface 
to control inflowing mine water. Most 
of the company's mine property has been 
mined out, except for a small 1-1/4— mi 2 
(3.24—km 2 ) area, which is currently ex- 
periencing water problems. It is not to 
the company's benefit to expend large 
amounts of money on well development and 
testing. However, it would be beneficial 
for the company to extract the existing 
coal, since it represents a considerable 
market value. Company officials have 
therefore decided to dewater the overbur- 
den by retreat mining the area between 
the water source and the workings , there- 
by creating a large sump where the water 
can be collected and pumped out of the 
mine. This type of system is extremely 
cost effective under conditions such as 
those at this mine. 



43 



OTHER CONSIDERATIONS 



Well dewatering systems are not de- 
signed to control or influence sudden in- 
rushes of water. Sudden inrushes are 
usually associated with one of the three 
following situations: (1) flood waters 
entering a mine opening located in the 
floodplain, (2) subsidence or caving be- 
low a large water body, or (3) breaching 
of an underground pool of water such as 
abandoned and flooded mine workings. Al- 
though a dewatering well can be used to 
drain abandoned flooded mine workings 
when they are identified, inrushes are 
usually associated with unidentified and 
unexpected underground pools. Conse- 
quently, well dewatering systems cannot 
be credited with providing any benefits 
in this area. 

Roof collapses, which are a reflection 
of poor roof conditions, are often asso- 
ciated with the presence of water in con- 
junction with geologic unconformities. 
Water will either soften claystone roof 
or act as a lubricant to decrease the 
frictional resistance to movement of rock 
strata. It has been postulated that well 
dewatering systems may aid in the control 
of roof problems by reducing the volume 
of water entering the working section. 
However, since dewatering systems have 
been demonstrated to intercept less than 
50 pet of the inflow to a given section, 
their benefit with respect to roof con- 
trol is questionable. Reducing inflow to 
a working section from 100 to 50 gpm (6.3 
to 3.2 L/s) is not likely to improve roof 
conditions significantly. Lubrication of 
a slip surface, such as a slickenslide, 
requires only small volumes of water or 
moisture, although the precise amount is 
variable. Thus, it would appear that in 
order to improve roof control problems, a 
dewatering system would have to intercept 
virtually all of the water coming in con- 
tact with slip or failure planes. Simi- 
larly, only small amounts of water are 
necessary to cause a softening of under- 
clays, which leads to floor heave and 
pillar punching. 

Ventilation problems associated with 
the presence and flow of water include 
increases in heat and humidity, and ven- 
tilation system blockages. The potential 



effect of well dewatering on heat and 
humidity has not been explored to date. 
However, with respect to ventilation sys- 
tem blockages, well dewatering systems do 
not appear to offer any advantages over 
conventional drainage systems. 

In summary, the use of a well dewater- 
ing system in the Appalachian coalfields 
is not likely to provide any substantial 
advantage over conventional drainage sys- 
tems with respect to health and safety. 

An underground coal mine has the poten- 
tial to substantially alter both the 
quantity and quality of surface and un- 
derground water. The impact of coal 
mines on water quality has been the focus 
of many research projects in the past. 
Regulation of the impact of coal mines on 
the quantity of both surface and ground 
water is a more recent development. 

The use of dewatering wells to control 
the contamination of water by underground 
coal mines is particularly attractive 
from an environmental standpoint because 
it eliminates the need for treatment pri- 
or to discharge to surface waters. For 
those underground mines involved in the 
handling, pumping, and treatment of large 
volumes of contaminated water, it might 
prove cost effective to intercept the 
mine inflow prior to contamination and 
release the uncontaminated water directly 
to surface streams, thus avoiding the 
cost of treatment. 

This practice is not directly ap- 
plicable in Appalachia for a number of 
reasons. There are wide variations in 
the characteristics of natural waters 
throughout the Appalachian coalfields. 
Simply because ground water is "natural" 
does not imply that State regulatory 
agencies will allow its discharge to sur- 
face streams without treatment. For ex- 
ample, the ground water encountered in 
case study 2 was derived from an acidic 
sandstone and displayed a natural pH in 
the range of 4.0 to 4.5. Consequently, 
this water would have to be treated to 
obtain a pH in the range of 6.0 to 9.0 
prior to release. In addition, the natu- 
ral ground water may be objectionable 
with respect to its iron, manganese, or 
dissolved salts concentrations. 



44 



A second major constraint to the suc- 
cessful application of this approach in 
Appalachia is the failure to demonstrate 
that it can result in well effectiveness 
(the ability to intercept a certain per- 
centage of the mine drainage inflow) ex- 
ceeding 50 pet [Fink (13)]. This method 
would require the use of two separate 
dewatering systems at the mine: the 
standard approach to mine dewatering, 
previously discussed, and the well dewa- 
tering system itself. 

Well dewatering systems appear to be 
more advantageous at shallower depths. 
In order to obtain a well effectiveness 
of 80 pet, the depth of the mine would 
have to average less than 220 ft (67 m) 
for the system to be cost effective ( 13). 
The average depth of underground coal 
mines in Appalachia is approximately 600 
ft (183 m) , and this value is expected to 
increase in the future. Consequently, it 
is unlikely the high well-effectiveness 
values can be achieved at this time, and 
the likelihood decreases in the future as 
the depths of mines increase. 

There is very little information avail- 
able on the cost effectiveness of well 
dewatering systems in Appalachian under- 
ground coal mines. In fact, the only 



information available is that provided in 
case study 1, which represents the only 
known and reported demonstration of such 
a system. 

The results of this demonstration pro- 
gram indicate that the cost of well dewa- 
tering appears to be, on the average, /at 
least twice that of present water removal 
and treatment practices. The case study 
suggests that dewatering with individual- 
ly pumped wells could be cost effective 
if the coal seam is less than about 150 
ft (45 m) deep. As previously discussed, 
the average depth of underground mines in 
Appalachia is approximately 600 ft (183 
m) , and that figure is expected to in- 
crease. There are very few underground 
mines with depths of less than 150 ft 
(45 m) in Appalachia. 

The case studies suggest that addition- 
al indirect benefits of dewatering, such 
as reduction of production losses due to 
high water inflows and unstable roofs, 
could enhance the effectiveness of well 
dewatering systems. However, the volume 
of water intercepted by the dewatering 
systems has not been demonstrated to in- 
crease productivity any more than conven- 
tional drainage methods. 



CONCLUSIONS 



IMPACTS OF MINE WATER 

The effects of mine water fall into 
four major categories, as follows: 

1. Health and Safety 



system can cause failure in weak shale 
roofs. 

• Mine water increases the maintenance 
requirements for both electrical and me- 
chanical equipment. 



• The concern for inrushes of mine wa- 
ter in Appalachia is likely to increase 
in the future as the number of new mines 
increases, particularly since these new 
mines will often be sited in the deeper 
seams, adjacent to and/or underlying the 
older water-logged workings. 

• Mine water can affect a mine's ven- 
tilation in two ways: it can (1) aggra- 
vate the heat and humidity problem and 
(2) block the ventilating airways. 

• Mine water seeping through the roof 
and moisture supplied by the ventilation 



• The presence of mine water, particu- 
larly when strongly acidic or alkaline, 
can accelerate the corrosion of mining 
equipment. 

2. Production 

• A survey of 325 working sections in 
the Appalachian region revealed that 56 
pet of the sections had floor conditions 
in the wet to damp category. Thirty-nine 
percent of these sections displayed floor 
conditions with some degree of rutting 
and probable rolling resistance exceeding 
100 lb/ton (51 kg/t). 



45 



• A correlation of these floor con- 
ditions with production suggested that 
a section would experience a decrease 
on the order of 16 to 25 tons (14.5 to 
22.7 t) per shift per drop in bottom 
classification. Thus, a difference in 
the range of 32 to 50 tons (29 to 45 t) 
per shift might be experienced between 
a section with a dry, hard floor and a 
section with a wet, rutted, and slippery 
floor. 

3. Environment 

• The mechanisms that cause hydrologic 
impacts include (1) the removal of the 
coal seam, which results in underground 
cavities that serve as broad sinks or un- 
derdrains , which receive ground water 
percolating downward from overlying 
strata, (2) the fracturing and separation 
of overlying strata resulting from the 
removal of the coal seam, and (3) the re- 
moval of the water from the mine by grav- 
ity drainage and pumping. 



• Recent inve 
hydrologic impact 
of domestic wel 
be a frequent oc 
for two reasons 
mining zone were 
mine depth excee 
(2) the average 
in Appalachia is 
and this figure 
future. 



stigations suggest that 
s , such as dewatering 
Is, are not likely to 
currence in the future 
: (1) wells above the 
not dewatered when the 
ded 300 ft (91 m), and 
depth of existing mines 
already 600 ft (183 m) , 
will increase in the 



4. Costs 

• A difference in coal sales ranging 
from $422,400 to $660,000 per mining sec- 
tion per year can be experienced between 
a section with a dry, hard floor and a 
section with a wet, rutted, and slippery 
floor. 

• Existing information on the effects 
of mine water on health and safety, pro- 
duction, environment, and costs is gen- 
erally qualitative. Very little quan- 
tification of these impacts has been 
attempted to date, which precludes the 
determination of associated costs. 



SOURCES OF INFLOW TO UNDERGROUND MINES 

In order to assess conditions where wa- 
ter diversion and overburden dewatering 
might be feasible, it is necessary to 
briefly evaluate the characteristics of 
the aquifers associated with coal seams 
at mine sites in Appalachia. However, 
the literature survey revealed that there 
is a general lack of such data. This 
study also indicated that there is a gen- 
eral lack of information on sources of 
water inflows in underground mines. 

The literature survey and consulta- 
tions with mine personnel revealed that 
fracture-dominated flow systems are the 
major source of water inflow in under- 
ground mines, especially with large mine 
inflows of ground water. Fracture zones 
associated with faulting, jointing or 
subsidence are the avenues 'for the larger 
inflows . 

WATER CONTROL METHODS 

Several methods were identified for 
controlling surface and ground water in- 
flow to underground mines , but the liter- 
ature evaluation revealed that the tech- 
nical feasibility and cost effectiveness 
of many of these methods have yet to 
be determined. A number of practices re- 
ported were developed or adapted for use 
in controlling water problems associ- 
ated with abandoned underground mines. 
Many of the practices were selected be- 
cause they represented the best, and in 
some instances the only, available con- 
trol technology. Provisions were seldom 
made, however, to monitor the short- or 
long-term performance of these control 
measures. 

CURRENT ENGINEERING PRACTICES 

Consultation with mine personnel re- 
vealed only one widely recognized and ac- 
cepted approach to managing the influx of 
water into underground coal mines in Ap- 
palachia. This approach consists of col- 
lecting the water that builds up within a 
section with one or more portable pumps 
and transferring it through a combination 
of conduits (either pipes or ditches), 



46 



sumps, and pumps back to a surface hold- 
ing facility for treatment and discharge 
to surface waters. As a consequence of 
this approach, the preferred method of 
planning an underground coal mine to min- 
imize water problems consists of develop- 
ing the mains along the strike of the 
coal. Panels are driven on the downdip 
during advance and on the updip during 
retreat. The investigations conducted 
during this project did not identify any 
new basic approaches that could replace 
the standard approach to mine dewatering 
described above. 

The use of water diversions and over- 
burden dewatering methods is not likely 
to control the flow of water into under- 
ground mines sufficiently to alleviate 
the need to develop a traditional system 
of gravity drainage and pumpage. These 
methods should not be viewed as alterna- 
tives, but rather supplements to tradi- 
tional methods of handling water in un- 
derground mines. 

To justify the application of water 
diversions and overburden dewatering, it 
is necessary to identify and quantify the 



benefits derived from the use of these 
control practices. These benefits must 
be greater than the benefits provided by 
the standard dewatering approach to jus- 
tify the additional expense. 

On the basis of reported data, the use 
of dewatering wells alone, drilled from 
the surface in advance of mining, does 
not appear to be a cost-effective method 
of dewatering underground coal mines in 
Appalachia, except under unusual condi- 
tions. These conditions include an aver- 
age depth of overburden above the coal 
seam not exceeding 200 ft (67 m) , inter- 
ception of 80 pet of the normal mine wa- 
ter inflow, and an acidity concentration 
in contaminated mine waters in the range 
of 500 to 700 ppm (500 to 700 mg/L). 

These are rather unusual circumstances 
in underground Appalachian coal mines, 
which average approximately 600 ft (183 
m) , a value which is projected to in- 
crease in the future. On this basis, it 
is concluded that the use of dewatering 
wells drilled from the surface in advance 
of mining is not practical at this time 
in Appalachia. 



RECOMMENDATIONS 



Methods of predicting water inflow to 
underground mines should be standardized 
and simplified. The regulatory require- 
ments of the Office of Surface Mining re- 
quire that a permit application for an 
underground coal mine include a determi- 
nation of the probable hydrologic conse- 
quences of the proposed mine plan area 
and adjacent area, with respect to the 
hydrologic regime and quantity and qual- 
ity of water in surface and ground water 
systems under all seasonal conditions 
[30 CFR 780.21(c)]. Particular emphasis 
should be placed on the feasibility of 
developing empirical values and constants 
on a regional or subregional basis, such 
as a drainage basin, to facilitate and 
simplify these computations. 



The Bureau's Bulletin 570, "Ameri- 
can Standard Recommended Practice for 
Drainage of Coal Mines (M6. 1-1955, UDC 
622.5)," needs to be updated. This pub- 
lication, published in 1957, provides the 
latest in formal guidelines for drainage 
practices of coal mines. The guidance 
provided should be reviewed and reas- 
sessed in order to incorporate any devel- 
opments that have occurred over the past 
23 yr and, in particular, to assess the 
compatibility of the recommended drainage 
practices with new regulatory require- 
ments such as those implemented by the 
Office of Surface Mining. 



REFERENCES 



47 



1. Ash, S. H. Water Problem in the 
Pennsylvania Anthracite Mining Region. 
BuMines IC 7175, 1941, 11 pp. 

2. Ash, S. H. , W. E. Cassap, W. L. 
Eaton, K. Hughes, W. M. Romischer, and 
J. Westfield. Flood-Prevention Projects 
at Pennsylvania Anthracite Mines. Prog- 
ress Report for Fiscal Year Ended June 
30, 1947. BuMines RI 4288, 1948, 51 pp. 

3. Ash, S. H. , H. A. Dierks , and P. S. 
Miller. Mine Flood Prevention and Con- 
trol: Anthracite Region of Pennsylvania. 
BuMines B 562, 1957, 100 pp. 

4. Ash, S. H. , and H. B. Link. Sur- 
face-Water Seepage Into Anthracite Mines 
in the Western Middle Field, Anthracite 
Region of Pennsylvania. BuMines B 532, 
1953, 26 pp. 

5. Ash, S. H. , H. B. Link, and W. M. 
Romischer. Surf ace-Water Seepage Into 
Anhracite Mines in the Southern Field, 
Anthracite Region of Pennsylvania. Bu- 
Mines B 539, 1954, 52 pp. 

6. Ash, S. H. , and R. H. Whaite. Sur- 
face-Water Seepage Into Anthracite Mines 
in the Wyoming Basin Northern Field, An- 
thracite Region of Pennsylvania. BuMines 
B 534, 1953, 30 pp. 

7. Bunting, D. The Limits of Mining 
Under Heavy Wash. Trans. AIME, v. 51, 
Feb. 1915, pp. 177-199. 

8. Coal Age. Coal Division Pumping 
and Drainage. V. 67, No. 10, Oct. 1962, 
pp. 125-127. 

9. Davies , A. W. , and W. K. Baird. 
Water Dangers. Min. Eng. (London), v. 
136, No. 188, Dec. 1976, pp. 175-184. 



10. Dierks, H. A., W. L. Eaton, R. H. 
Whaite, and F. T. Moyer. Mine Water Con- 
trol Program, Anthracite Region of Penn- 
sylvania: July 1955 — December 1961. Bu- 
Mines IC 8115, 1962, 63 pp. 

11. Doll, W. L. , G. Meyer, and R. J. 
Archer. Water Resources of West Vir- 
ginia. WV Dep. Nat. Resour. , Div. Water 
Resour. (in cooperation with U.S. Geol. 
Surv.), 1963, 134 pp. 

12. Doyle, F. J., C. Y. Chen, R. D. 
Malone, and J. R. Rapp. Investigation of 
Mining Related Pollution Reduction Activ- 
ities and Economic Incentives in the 
Monongahela River Basin (Appalachian Re- 
gional Comm. contract ARC-72-89/RPC-707, 
Michael Baker, Jr., Inc., Beaver Falls, 
PA). 1975, 416 pp. 

13. Fink, G. B. Cost Effectiveness 
of Aquifer Dewatering. Paper in Coal 
Conference & Expo V (Symp. on Underground 
Mining, Louisville, KY, Oct. 23-25, 
1979). McGraw-Hill, 1979, pp. 147-157. 

14. Gulati, A. K. , and A. K. Singh. 
Scheme of Developing Seams Below Water 
Logged Workings. J. Mines, Met., and 
Fuels, v. 25, Jan. 1977, pp. 3-8. 

15. Johnston, W. D. , Jr., M. D. Fos- 
ter, and C. S. Howard. Ground Water in 
the Paleozoic Rocks of Northern Alabama. 
AL, Geol. Surv. (in cooperation with U.S. 
Geol. Surv.), Spec. Rep. 16, 1933, pt. 2, 
58 pp. 

16. Kenny, P. Corrosion Effects of 
Mine Waters. Paper in Proc. Symp. on En- 
vironmental Engineering in Coal Mining 
(London, Oct. 31-Nov. 2, 1972). Inst. 
Min. Eng., London, 1972, pp. 165-175. 



48 



17. Klingensraith, R. S. , A. F. Miorin, 
and J. R. Saliunas. At Source Control 
Through the Application of Several Abate- 
ment Techniques. Paper in Sixth Sympo- 
sium on Coal Mine Drainage Research 
(Louisville, KY, Oct. 1976). Bituminous 
Coal Res., Inc., Monroeville, PA, 1976, 
pp. 270-284. 

18. Lohman, S. W. Ground Water Re- 
sources of Pennsylvania. PA, Topogr. and 
Geol. Surv. (in cooperation with U.S. 
Geol. Surv.), Bull. W 7, 1941, 32 pp. 

19. Lovell, H. L. , and J. W. Gunnett. 
Hydrogeological Influences in Preventive 
Control of Mine Drainage From Deep Coal 
Mining (PA Dep. Environ. Resour. contract 
EER-114). PA State Univ., Dep. Miner. 
Eng. , University Park, PA, Spec. Res. 
Rep. SR-100, May 1974, 89 pp. 

20. Manula, C. B. , A. Bouillot, 
R. Rivell, and R. Sandford. Production 
Subsystem. U.S. Dep. Commerce, v. 6, 
1974, 356 pp.; NTIS PB 255 424/ AS. 

21. Mason, W. A. Electrical Hazards 
in Underground Bituminous Coal Mines. 
MESA (now MSHA) , U.S. Dep. Labor, Inf. 
Rep. 1018, 1975, 5 pp. 

22. Miller, J. T. , and D. R. Thompson. 
Seepage and Mine Barrier Width. Paper in 
Fifth Symposium on Coal Mine Drainage 
Research (Louisville, KY, Oct. 1974). 
Natl. Coal Association, Pittsburgh, PA, 
1974, pp. 103-117. 

23. Parizek, R. R. Prevention of Coal 
Mine Drainage Formation by Well Dewater- 
ing. PA State Univ., Dep. Geol. and Geo- 
phys., University Park, PA, Spec. Res. 
Rep. SR-82, April 1971, 73 pp. 

24. Parizek, R. R. , J. Sgambat, and 
M. Clar. Geology and Related Natural 
Resources of the Eastern Coal Fields. 
User's Manual for Premining Planning of 
Eastern Surface Coal Mining, v. 3, (U.S. 
EPA grant R803882, PA State Univ., Col- 
lege of Earth and Miner. Sci.). EPA-600/ 
7-81-022, Mar. 1981, 344 pp. 



25. Parizek, R. R. , and E. G. Tarr. 
Mine Drainage Pollution Prevention and 
Abatement Using Hydrological and Geo- 
chemical Systems. Paper in Fourth Sym- 
posium on Coal Mine Drainage Research 
(Pittsburgh, PA, Apr. 1972). Bituminous 
Coal Res., Inc., Monroeville, PA, 1972, 
pp. 56-82. 

26. Peters, T. W. Mine Drainage Prob- 
lems in North Derbyshire. Paper in Proc. 
General Meeting of the Notts and North 
Derbyshire Branch of I Mine, Mines Rescue 
Station (Mansfield, England, Jan. 1977). 
Natl. Coal Board, London, 1977, pp. 462- 
472; Min. Eng. (London), v. 137, No. 200, 
Mar. 1978, pp. 463-473. 

27. Rauch, H. Effect of Underground 
Mining on Water Wells in Monongalia Coun- 
ty, West Virginia. Paper in Proceedings 
of the Fourth National Symposium on Aqui- 
fer Restoration and Ground Water Monitor- 
ing (Natl. Water Well Exposition, Colum- 
bus, OH, Sept. 20, 1978). Natl. Water 
Well Association, Worthington, OH, 1978, 
pp. 88-96; J. Ground Water, v. 16, No. 5, 
1978, p. 358 (abstr.). 

28. Schmidt, R. D. , and G. Ahnell. A 
Fracture Dewatering Approach to Controll- 
ing Groundwater Infiltration in Under- 
ground Coal Mines (Interim Report) . Bu- 
Mines, Jan. 1983, 184 pp.; available upon 
request from R. D. Schmidt, Twin Cities 
Res. Cent., Minneapolis, MN. 

29. Scott, L. R. , and R. M. Hays. In- 
active and Abandoned Underground Mines — 
Water Pollution Prevention and Control 
(U.S. EPA contract, Michael Baker, Jr., 
Inc., Beaver Falls, PA). EPA-440/9-75- 
007, June 1975, 338 pp. 

30. Sgambat, J., E. A. Labella, and 
S. Roebuck. Effects of Underground Coal 
Mining on Ground Water in the Eastern 
United States (U.S. EPA contract 68-03- 
2467, Geraghty and Miller, Inc., Syos- 
set, NY). EPA-600/7-80-120, June 1980, 
183 pp. 



49 



31. Shotts, R. Q. , E. Sterett, and 
T. A. Simpson. Site Selection and Design 
for Minimizing Pollution From Underground 
Coal Mining Operations (U.S. EPA contract 
68-03-2015, Univ. AL, University, AL). 
EPA-600/7-78-006, Jan. 1978, 98 pp. 

32. Skelly and Loy. Guidelines for 
Mining Near Water Bodies. Phase III. 
Recommended Guidelines for Mining Under 
Surface Waters (contract H0252083) . Bu- 
Mines OFR 29-77, 1976, 193 pp.; NTIS PB 
264 728/ AS. 

33. Slaughter, T. H. , and J. M. Dar- 
ling. The Water Resources of Allegheny 
and Washington Counties. MD, Dep. Geol. , 
Mines and Water Resour. , Bull. 24, 1962, 
408 pp. 

34. Stefanko, R. Coal Mining Tech- 
nology - Theory and Practice. Soc. Min. 
Eng. AIME, Littleton, CO, 1983, 402 pp. 

35. Suboleski, S. C. Effects of Phys- 
ical Conditions on Continuous Mine Pro- 
duction in Underground Coal Mines. Ph.D. 
Thesis, PA State Univ., University Park, 
PA, 1978, 362 pp. 

36. Todd, D. K. Ground Water Hydrol- 
ogy. Wiley, 1959, 336 pp. 

37. UOP, Inc. , Johnson Division (St. 
Paul, MN). Ground Water and Wells. 4th 
ed. , 1975, 440 pp. 

38. Wahler, W. A., and Associates. 
Dewatering Active Underground Coal Mines: 
Technical Aspects and Cost Effectiveness 
(U.S. EPA contract). EPA-600/7-79-124, 
July 1979, 124 pp. 



39. Walton, W. C. Leaky Artesian 
Aquifer Conditions in Illinois. IL State 
Water Surv. , Rep. Invest. 39, 1960, 
27 pp. 

40. Wardell, K. , and Partners. Guide- 
lines for Mining Under Surface Waters. 
Phase III and Final Report (contract 
H0252021). BuMines OFR 30-77, 1976, 67 
pp.; NTIS PB 264 729/ AS. 

41. White, P. E. Corrosion Research 
and Corrosion Resistance Fasteners. Min. 
Eng. (London), v. 127, No. 92, May 1968, 
pp. 463-473. 

42. Whittaker, B. N. , R. N. Singh, and 
C. J. Neate. Investigation and Evalua- 
tion Studies of Surface and Subsurface 
Drainage Pattern Changes Resulting From 
Longwall Mining Subsidence. Paper in 
Mine Drainage (Proc. 1st Int. Mine Drain- 
age Symp., Denver, CO, May 1979). Miller 
Freeman Publ. , Inc., 1979, pp. 161-183. 

43. Wilson, L. W. , N. J. Mathews, and 
J. L. Stump. Underground Coal Mining 
Methods To Abate Water Pollution: A 
State of the Art Literature Review (U.S. 
EPA, project 14010 FKK, Coal Res. Bureau, 
Morgantown, WV). Dec. 1970, 178 pp. 

44. Wrathers , R. J., A. W. Swanson, 
and R. F. Langill. Investigation and 
Analysis of Subsurface Conditions for 
Coal Mine Development in Eastern Ken- 
tucky. Paper in 19th U.S. Symposium on 
Rock Mechanics (Stateline, NV, May 1978). 
Univ. NV-Reno, 1978, pp. 151-158. 



50 



APPENDIX A. —CASE STUDY 1 



INTRODUCTION 

The interception of ground water in- 
flows to active coal mines was the sub- 
ject of a study conducted by W. A. Wahler 
and Associates for the Environmental Pro- 
tection Agency (38). 1 The study involved 
the construction and operation of a pilot 
well dewatering system, to collect and 
analyze both technical and cost data. 
The study site for this pilot dewatering 
program was the Lancashire No. 20 Mine, 
located near Carrolltown, PA, and owned 
by the Barnes and Tucker Co. (fig. A-l). 
The Lancashire No. 20 is a moderately 
deep slope mine, and the Lower Kittanning 
(B) coal of the Allegheny Group is the 
only seam mined. The coal seam averages 
60 in (152 cm) in thickness and is lo- 
cated at depths ranging from 500 to 550 
ft (152 to 168 m) in the vicinity of the 

1 Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding this appendix. 



PA 



r^\. 



Mine property boundary 



v.r'Vh'a'g 




Carrolltown , 
^(study site)( 



Study area 



^Eastern working 
I n face 




&J 



Scale, miles 



FIGURE A-l. - Location map of Lancashire 
No. 20 Mine and pilot well dewatering site. 



study area. The "B" coal is metallurgi- 
cal-grade, low-sulfur, low-volatile coal. 
The longwall method of mining is used. 

The objectives of the pilot study were 
(1) to determine the impact of the dewa- 
tering operation on the quantity and 
quality of inflows in the limited area 
of the mine under study, (2) to evaluate, 
by extrapolating the results of this pro- 
gram, the potential effectiveness of the 
dewatering technique for the mine as a 
whole, and (3) to perform an economic 
evaluation of the technique. 

GEOLOGIC ENVIRONMENT 

Surface Geology 

Unconsolidated materials cover most of 
the surface of the area and include qua- 
ternary alluvium, colluvium, and seden- 
tary soil. Sedentary soil and colluvium 
make up the greater percentage of this 
cover and typically consist of silty sand 
to silty clay. They form a soil cover 
over bedrock units that varies widely in 
thickness. Quaternary alluvial material 
consists chiefly of sandy silt and sand. 
This alluvium is restricted to the flood- 
plain and channel of Laurel Lick Run, 
which runs across the mine property. 

All rocks exposed on the surface are 
of Pennsylvanian age and belong to the 
Glenshaw Formation of the Conemaugh 
Group. They generally consist of thinly 
to thickly bedded sandstone and shale. 
Sandstones are generally quartzose and/or 
argillaceous, fine to very fine grained, 
moderately hard to very hard, moderate- 
ly weathered, and iron oxide stained. 
Shales are gray to gray brown, moderately 
hard, and moderately to severely weath- 
ered. The outcrops of sandstone and 
shale are relatively few in number and 
are generally covered by soil units. 

Subsurface Geology 

A generalized stratigraphic column of 
the units encountered is shown in fig- 
ure A-2. All rocks in the subsurface 
are from Pennsylvanian period and are 



51 



DEPTH, ft 
O-i 



100- 



Lithology Description 



200- 



300- 



- : : - 



?: :- 



600- 



-"- 







a. 


c 
o 










o 


o 




O 


E 




f 


.? 




o> 






3 
O 

F 


3 




s> 


in 










o 






o 


O 


s 






_ 






£ 






>- 






to 






z 






< 






z 
< 










> 






_j 






>- 




o 


CO 






z 




o 


z: 




b 


111 
a. 




£ 




a. 


o 




3 


a. 




o 


a> 




— 


a> 




o 


it 




>> 












a> 


c 




c 


o 




o> 






■ 


a 




< 


E 

W 

£ 

— 
- 

c 
o 

2 




-^-~r 



Colluvium clayey sand 
Saltsburg Sandstone 

Shale, limestone 

Buffalo Sandstone, Siltstone 
Shale 

Brush Creek Marine shale 
Brush Creek Coalbed 
Corinth Sandstone 

Shale 

Mahoning Sandstone 

Upper Freeport Limestone 

Interbedded shale, siltstone, 

and sandstone 
Lower Freeport (D) Coalbed 

Interbedded shale, siltstone, 
and sandstone 

Upper Kittanning(C) Coalbed 
Upper Worthington Sandstone 

Shale 

Middle Kittanning(C) Coalbed 

Lower Worthington Sandstone 

Lower Kittanning (B)Coalbed 



FIGURE A-2. - Generalized strat igraph ic 
column, case study 1 . 

sedimentary in origin. Sandstone, shale, 
siltstone, limestone, coal, and clay were 
found. 

The rocks in the subsurface can be di- 
vided into two stratigraphic groups: the 
Allegheny and the Conemaugh. The Alle- 
gheny Group, the older of the two, can 
be further divided into three forma- 
tions (oldest to youngest): the Clarion, 
the Kittanning, and the Freeport. The 
maximum thickness encountered in the 
wells for the Allegheny Group was 250 ft 
(76 m). 

The Conemaugh Group overlies the Alle- 
gheny and can be divided into two 
formations: the Glenshaw and the Cas- 
selman. The Casselman Formation is 



stratigraphiically higher than the Glen- 
shaw and was not encountered on the 
surface or in the subsurface. The maxi- 
mum thickness for the Glenshaw Forma- 
tion was 328 ft (10° m) . Names of mem- 
bers for both the Allegheny and the 
Conemaugh Groups, along with relative 
thicknesses, are indicated on the strati- 
graphic column. 

Structurally, the area is generally 
flat with a gentle dip to the east- 
southest. Strata lie subparallel to one 
another except for the lowermost coal 
seam, the Lower Kittanning (a member of 
the Kittanning Formation of the Alle- 
gheny Group) , which dips to the east at a 
slightly greater angle. No fault fea- 
tures were identified by correlation of 
geologic units. 

HYDR0L0GIC CONDITIONS 

Surface Water 

The mine area lies within the drainage 
basin of the Susquehanna River, whose 
flow ultimately reaches the Atlantic 
Ocean. Laurel Lick Run and Chest Creek 
both cross the mine property. Laurel 
Lick Run, with a drainage area of 9 mi 2 
(23 km 2 ), flows into Chest Creek, which 
in turn flows into the West Branch of the 
Susquehanna River. 

Laurel Lick Run and Chest Creek are 
relatively unpolluted and support trout 
and other aquatic life. In the past, 
Chest Creek has been used as a source of 
municipal water and could be used in this 
manner in the future. Because of the 
high quality of water in this watershed, 
treated mine drainage from the Lancashire 
No. 20 Mine is discharged into the West 
Branch of the Susquehanna, though Laurel 
Lick Run is closer. 

Seeps, springs, and other hydrologic 
features are also present. Springs are 
few in number and not associated with any 
given horizon or topographic elevation. 
Only flows that are continuous year round 
were designated as springs, and flows for 
these are generally greater than 5 gpm 
(0.315 L/s). Seeps, on the other hand, 
were found to be quite common. Flow is 
usually less than 1 to 2 gpm (0.063 to 



52 



0.126 L/s), occurs intermittently, and is 
associated with wet periods. Seeps are 
commonly found in the topographic lows or 
swales or in areas with a break in slope. 

Ground Water 

Attempts were made to identify the 
principal water-bearing zones as they 
were encountered during air-rotary drill- 
ing. This was achieved by logging both 
the amount of water airlifted as the 
holes advanced and the rock types. Each 
water-bearing zone generally increased 
the amount of water airlifted as long 
as circulation was maintained. It was 
found, generally, that there was little 
correlation between rock types and the 
amount of ground water. There appeared 
to be some perching of ground water in 
the Saltsburg Sandstone, a member of the 
Glenshaw Formation of the Conemaugh 
Group, and possibly in the underlying 
unidentified limestone. Below this ap- 
parent perched zone, the bedded rock 
units could not be separated into dis- 
tinct aquifers or zones with any degree 
of consistency. In particular, the vari- 
ous sandstone beds encountered did not 
indicate higher permeabilities than even 
the shales. There were some indications 
that the coal seams and the Upper Free- 
port Limestone are relatively permeable, 
but not with consistency. Also, there 
were indications that the thin shale bed 
above the Lower Kit tanning (B) Coal, 
which forms the mine roof, is relatively 
permeable. This information, although 
not conclusive in itself , seems to indi- 
cate that fractures control the ground 
water flow. 

Pump test data indicated a very asym- 
metric drawdown response with the cone of 
depression around the pumped well elon- 
gated along fractures, possibly in sev- 
eral directions. Also, it was observed 
that there was very rapid response to 
heavy rainfall both in well water levels 
and in inflows to the mine, indicating a 
hydraulic connection of fracture zones 
with the surface. 

Using time-drawdown data from the 
pumped wells and distance— drawdown data, 
the transmissivities were calculated; 
they ranged between 200 and 300 gpd/ft 



(0.29 to 0.43 cm 2 /s). This was later 
confirmed using data developed from the 
pilot dewatering operation. 

In conclusion, the data strongly indi- 
cate that ground water drains into the 
study area along narrow, preferred flow 
paths. These flow paths are controlled 
by fractures and are directionally ori- 
ented. Permeabilities across these flow 
paths may be several orders of magnitude 
lower than permeabilities along the frac- 
ture planes. The bedded rock units prob- 
ably act as secondary aquifers to various 
degrees and provide both hydraulic inter- 
connection between fractures and ground 
water storage space. The fracture zones 
appear to consist mainly of steeply dip- 
ping fractures that intersect the sur- 
face. These permit rapid recharge from 
direct precipitation and from streams or 
ponds at the surface. The secondary 
aquifers also release ground water from 
storage to the fracture zones. The 
ground water flow regime is, therefore, 
quite complex and difficult to model with 
mathematical techniques because of the 
severe boundary effects and directional 
variations in permeability. 

MINE WATER 

The source of water inflow to the mine 
is ground water in overlying and sur- 
rounding rocks. Water flows into the 
mine primarily through the roof and is 
transmitted predominantly by fractures. 
There is probably some inflow through the 
mine floor, but it appears to be rela- 
tively minor. The mine floor is on an 
underclay (clay-shale) that restricts up- 
ward seepage of water. 

Although minor drips and seeps are 
scatterd throughout the mine, the larger 
inflows are localized, probably along 
zones of more intense fracturing. Frac- 
tures and fracture zones are caused orig- 
inally by geologic processes and later by 
the subsidence of rocks overlying the 
mine openings. Natural fractures were 
encountered while driving main haulage- 
ways and while establishing entries and 
crosscuts during the development of long- 
wall panels for mining. Unstable roofs 
are often associated with areas of rela- 
tively high water inflow. 



53 



Inflows to the longwall panels and 
abandoned areas of the mine are influ- 
enced both by natural fractures and sub- 
sidence fractures. The longwall panels 
are 500 to 550 ft (152 to 168 m) wide and 
about 3,500 ft long. Normally, all of 
the coal is extracted in a continuous 
operation, and the roof support is moved 
forward with the coal cutting machine, 
allowing the roof behind the support 
to collapse. Entries previously driven 
along the panel partially dewater the 
panel area, but new fractures associated 
with roof collapse, along with preexist- 
ing fractures, promote more drainage into 
the mine. New fractures may extend to 
the surface, resulting in drainage of 
ground water that was not previously 
tapped. These fractures can result in 
inflows of water that are large enough to 
cause handling problems and that have hy- 
drostatic heads sufficient to affect the 
caving characteristics of the roof. Both 
of these problems can affect production. 
Similarly, additional fracturing can be 
caused by the slow collapse of abandoned 
or inactive openings in which roof sup- 
ports have not been maintained. 

It appears that approximately 40 pet of 
the water enters through abandoned parts 
of the mine and 60 pet enters directly 
into the more recent workings. Inflows 
are affected by seasonal conditions, and 
it is even possible to recognize recharge 
from individual rainstorms. There is a 
tendency for high inflows to occur be- 
neath stream channels, which probably 
tend to follow fracture zones along parts 
of their courses. Wells and springs 
overlying the mine may be affected or 
drained completely, especially where sub- 
sidence has occurred. 

Water Removal 

Water in the mine is collected and 
transferred through a series of sumps and 
conduits and eventually pumped to the 
surface. Initially, water is collected 
by small sludge pumps or allowed to drain 
by gravity into sumps. From there it is 
pumped from sump to sump through pipe- 
lines, as shown schematically in figure 
A-3. Water is pumped to the surface from 
F-l and F-14 sumps, and the pipelines are 



combined to a single flow at the treat- 
ment plant, which has a design capacity 
of 5 million gpd (19 million L/d). Flow 
to the plant is controlled by pump opera- 
tors underground, according to water lev- 
els in the sumps. Logs are kept for each 
pump and are used to determine flow 
rates, based on the pump curves for the 
two sumps. 

Water Inflow Rate 

General 

Figure A-4 is a graph of average daily 
inflows to the treatment plant. The pat- 
tern of these flows tend to follow the 
dry and wet periods for this region. The 
yearly average flow for the period July 

1976 through June 1977 is 3.4 million gpd 
(12.9 million L/d). The data after June 

1977 are not reflective of normal flows, 
owing to the flooding on July 19 and 20 
and cleanup operations extending well in- 
to August 1977. 

Underground Study Area 

The underground test site is referred 
to as the Main G study area and is lo- 
cated near the northeasternmost limit of 
workings along Main G heading or (as com- 
monly referred to in the mine) the left 
side of Main G, near section G-14. The 
study area is bounded by the haulageway 
on the south, by the edge of underground 
working on the north and east, and by the 
G-ll entry on the west. Figure A-5 is a 
map of this portion of the mine. 

This area was selected because it has 
relatively high ground water inflows [ap- 
proximately 100 to 150 gpm (6.3 to 9.5 
L/s)] and because it could easily be sep- 
arated from other mine drainage and moni- 
tored. Mining in the immediate area had 
been temporarily halted because of unsta- 
ble roof conditions and high ground water 
inflows, so advancement of the workings 
would not hamper the progress of the 
project. 

Water enters the study area of the mine 
from the roof and from the coal seam. 
The roof is a gray to dark gray-brown 
shale-siltstone , which is fractured to 
intensely fractured. Slickensides and 



54 



L-2 
sump 



Drainage collected from Main G 
study area 



G-ll 
sump 



K-12 
sump 




G-IO 
sump 



6-9 

sump 



G-7 
sump 



G-5 
sump 



K - 7 sump 



F-20 
sump 



MainH 
sump 



LT 



F-13 
sump 



F-17 
sump 



Slant sump 



I 



Main Fsump, 

old workings 

drainage 



F-14 
sump 



—Old workings 
I drainage 

i 4. 



F-l 
sump 



i 



To treatment 

FIGURE A-3. - Water transport system. 



Main C 
sump 



Out- 
drift 



E 
a. 
en 



5.0 



CD 
O 



4.5- 



- 4.0 



UJ 





Unseasonably high flow due \ 

to pumping out mine following \ 

July 19-20, 1977, flood / 



Mar. 



May 



July Sept. 



I976 I977 

FIGURE A-4. - Average daily flows to treatment plant. 



55 



L-2 pool. 



Small pond 
L-4 



11 



n 

i UI| i 

» i 



m. 



\ 



? 



111 



^L-2 
sump 



Section 
G-14 



o 



tic 



Section 
G-ll 



G-ll 
sump 



^ 



LEGEND 
i— Light inflow 
°— "-Moderate inflow 
*—* Heavy inflow 
-*-— Direction of uncontained 

flow 
— —Direction of piped flow 
M Concrete block dam 
Pi Pump 



D 



100 



Scale, ft 



FIGURE A-5. - Main G study area. 



polished surfaces are common on much of 
the rock, and water drains freely from 
these fractures. Fractures in the roof 
rock are common throughout this area of 
the mine. Water inflow, however, tends 
to be more localized in areal extent. 
The shale-siltstone roof is about 7 ft 
(2 m) thick and is overlain by a massive 
sandstone. Originally, it was thought 
that this sandstone was acting as an 
aquifer and was the source of ground wa- 
ter inflow to the study area. However, 
drilling and pump testing indicated that 
this unit is relatively tight, except 
along fractures. 

The area of greatest mine inflow is 
along the L-4 heading near the northern 
face (see figure A-5) where most of it 
is collected behind a cement block dam. 
Overflow from the L-4 pond and any addi- 
tional drainage from the left (north) 
side of the Main G heading is collected 
in a low area of the mine floor, forming 



a pool located at the east end of the L-2 
heading. Prior to establishment of the 
underground monitoring system, the L-2 
pool also collected drainage from the 
right (south) side of the Main G head- 
ing. Water from both the L-4 pond and 
L-2 pool is then transferred to the L-2 
sump, which is formed by a cement block 
dam and is also located in the L-2 head- 
ing. Gravity flow is used to drain the 
L-4 pond, while pumping is required to 
remove water from the L-2 pool. Water 
collected in the L-2 sump includes all of 
the mine inflow to the Main G study area. 
From the L-2 sump, water is pumped to the 
G-ll sump where it is combined with wa- 
ter from adjacent areas and transferred 
through the mine and eventually to the 
surface. 

Flow measurements at the underground 
monitoring station began in the late part 
of September 1976. Figure A-6 represents 
typical background flow data for the to- 
tal water inflow occurring in the Main G 
study area of the mine. The data shown 
are average weekly values and the stan- 
dard deviation for each 7-day period. 
These data are based on average daily 
flows derived from individual flowmeter 
readings and have been adjusted for 
changes in L-2 sump water levels where 
appropriate. 

The average inflow rate for the entire 
period of September 26, 1976, through May 
31, 1977, was 106 gpm (6.7 L/s), with a 
standard deviation of 9 gpm (0.57 L/s). 
As can be seen in figure A-6, the water 
inflow did vary somewhat over time, but 
such changes were generally gradual. 

PILOT DEWATERING SYSTEM 

Method of Approach 

The objective of the dewatering program 
was to intercept a major portion of the 
ground water inflow to the Main G study 
area and to analyze the cost effective- 
ness of mine dewatering as a means of 
controlling acid mine drainage (AMD). 
Vertical wells were constructed adjacent 
to the mine openings to intercept ground 
water before it could be degraded in the 
mine. The wells were located along a 
line parallel to the mine face, in an 



56 



e 

Q. 



UJ 

I 

_j 

Li- 



150 



140 



130 



- 120 



10 



100 



90 



80 



'Standard 
deviation 





Sept. 



Oct. Nov. 
1976 



Dec. 



Jan. 



Feb. 



Mar. Apr. 
1977 



May 



June 



FIGURE A-6. - Average mine inflow in Main G study area. 



attempt to create a hydraulic drawdown 
barrier against ground water movement to- 
ward the underground study area. 

Results 



The first pilot dewatering started on 
July 13, 1977, pumping from wells P-l, 
P-2, and P-3 (shown in figure A-7). The 
yield of the wells was increased gradual- 
ly to a maximum total of 45.5 gpm (2.9 
L/s). This yield was disappointing, be- 
cause P-l and P-3 were each expected to 
yield 40 to 50 gpm (2.5 to 3.2 L/s) on 
the basis of previous pump tests. Well 
P-2 did not produce much water and was 
later removed. Pumping continued for 
about 3 days and was stopped on July 16. 
During this period, flows in the Main G 
study area of the mine had decreased from 
107 to 96 gpm (6.75 to 6 L/s), or 10 pet, 
as shown in figure A-8. About 24 pet of 
the water pumped from the wells was in- 
tercepted or diverted from the mine. 
These results were somewhat improved 
by an equipment change. 



A 

u- 

p-4(0B-4) 



P-3 



tr !° B - 3 ^T 




LEGEND 
• Pumping well 
o Observation well 







400 



Scale, ft 

FIGURE A-7. - Location map of dewatering 
and observation wells. 

The 5-hp pump was removed from P-2 
and installed in observation well 0B-4, 
thereafter designated P-4. Pumping 



57 



resumed on July 18, and total pumpage was 
increased to 73.5 gpm (4.6 L/s). On July 
19, flow in the Main G study area, which 
had increased to 111 gpm (7 L/s) just 
prior to restarting the pumps, rapid- 
ly decreased 23 pet to about 85 gpm (5 
L/s). This indicated that 35 pet of the 
water pumped from the wells was diverted 
from mine inflows. The operation was 
interrupted by mine flooding, but these 
results were encouraging because the per- 
centage of water intercepted should 
increase with time. 

Dewatering was again resumed on Sep- 
tember 16, 1977, after the wells were 
cleaned and the pumps were reset. The 
average total pumpage was approximately 
82 gpm (5.2 L/s), ranging from about 95 
gpm (6 L/s) near the start to about 75 
gpm (4.7 L/s) at the end of the pumping 
period. Well OB-1 responded as expected, 
with generally consistent declines dur- 
ing pumping except near the end of the 
period. Well OB-2 declined rapidly at 
first and then more or less stablized. 
Water levels in P-2 declined slightly and 
then rose. Well OB-3 had essentially no 
response to pumping. 

Inflows to the Main G study area (fig. 
A-9) decreased rapidly at first but 
showed only a slight decreasing trend 
after September 25. Inflows ranged from 
70 to 76 gpm (4.4 to 4.8 L/s) after this 
date and quickly recovered to 112 gpm (7 
L/s) after pumping stopped. The average 
inflow rate from September 25 through 
October 6 was 73.2 gpm (4.6 L/s), with a 
standard deviation of ±1.92 gpm (±0.12 

120 



!l no 
uT 

< 100 
£T 

o 

.T 1 90 



90 



Start P-3 and 
P-4 (0B-4) 



Start 



Start P-l, 
Start P-3 




Shut off P-l. P-2, 
and P-3 



Pumping discontinued, 
mine flooding 



— 



— 



J L 



9 10 II 12 13 14 15 16 17 18 19 20 
July 

FIGURE A-8. • Average daily mine inflow, July 
1977. 



L/s). The postpumping monitoring peri- 
od, after inflows had recovered, from 
October 8 through October 22, showed an 
average flow of 110 gpm (6.9 L/s), with 
a standard deviation of ±4 gpm (±0.25 
L/s). These values are comparable to 
all of the other background data, which 
showed an average inflow rate of 112±9.4 
gpm (7±0.59 L/s). 

All of the pumping and observation 
wells, with the exception of 0B-2, were 
affected by recharge from direct precipi- 
tation. The pumping and inflow data in- 
dicate that the mine study area inflow 
was decreased by about 34 pet, based on 
average flow rates. This decrease may 
have been as much as 38 pet, based on 
measurements at the end of the pumping 
period and the first inflow measurements 
after full recovery. These data indicate 
that 45 pet of the water pumped from 
wells comprised intercepted or diverted 
mine inflow, based on average rates for 
the pumping period. Theoretically, this 
percentage should increase with time, and 
at the end of the test, up to 56 pet of 
the water pumped was diverted from mine 
inflows. Projection of these data to 120 
days of pumping indicated that up to 80 
pet of the water pumped would be diverted 
from mine inflows. Recharge from storms 
or streams would reduce these percent- 
ages. Therefore, for purposes of esti- 
mating full-scale mine dewatering, it was 
assumed that 50 to 80 pet of the water 
yield from dewatering wells would be di- 
verted from mine inflows. 

During the dewatering operation, well 
yields were still disappointing. Only 
well P-3 was close to the maximum avail- 
able drawdown, and that could not be 
sustained during the latter part of the 
pumping period. Well P-l had more than 
100 gpm (6.3 L/s) of available additional 
drawdown. The 7.5-hp pump in each of 
these two wells was not able to produce 
at Its rated capacity, which was in ex- 
cess of 40 gpm (2.5 L/s), with a pump 
lift of 510 ft (155 m). In contrast, 
the 5-hp pump performed relatively well 
throughout most of the dewatering program 
and during earlier pump tests. Howev- 
er, the yield of well P-4 gradually de- 
creased, along with a small increase in 
drawdown. The impellers on the 7.5-hp 



58 




Pumping ended 
Oct. 7, 9a.m. 



/Standard deviation 
J I I I L_L 



16 18 20 22 24 26 28 30 2 4 6 8 10 12 14 16 18 20 22 24 

Sept. Oct. 

FIGURE A-9. - Average daily mine inflow, September 1977. 



pumps may have been worn, reducing their 
capacity, or gas blocks may have devel- 
oped to retard well yield. Although it 
was detected that all three pumping wells 
produced methane gas , the volume was not 
measured. The pumped water obviously had 

Cost 



a large amount of gas entrained in the 
discharge. 

For the study mine, costs 
collection and treatment were 
from company records: 



for water 
computed 



Collection 



Treatment 



Capital investment $432,000 $430,000 

Operating costs: 

Annual 530,000 209,000 

Per 1,000 gal 1 .468 

'Based on average flow rate of 3.1 million gpd. 



.185 



Of the $530,000 annual operating cost for 
water collection, approximately 77 pet 
goes for water collection and transfer 
costs, and 23 pet for pumping to the sur- 
face. Major cost contributors to the 
$530,000 are power, 37 pet, labor, 36 



pet, material, 19 pet, and other charges, 
8 pet. 

The computed values of treatment plant 
capital costs ($430,000) and annual oper- 
ating expenses for treatment ($209,000) 
compare reasonably well with figures from 



59 



published sources for other plants of 
similar capacity treating water with sim- 
ilar flow rates and acid levels. 

Individually pumped wells constructed 
from the surface, as used in this study, 
do not appear to be cost effective in 
controlling water quality at the Lan- 
cashire No. 20 Mine, unless the average 
well yield can be increased three to four 
times the 30 gpm (1.9 L/s) used in the 
analyses. The cost of well dewatering at 
this mine appears to be, on the average, 
at least twice as great as present wa- 
ter removal and treatment costs. If the 
acidity of the mine water were higher (in 
the range of 500 to 1,500 ppm — 500 to 
1,500 mg/L) this dewatering system would 
be more cost effective. Also, if the 
coal seam were less than about 150 ft (46 
m) deep, it appears that it would be fi- 
nancially feasible to dewater using indi- 
vidually pumped wells. Conservative well 
yields were used in the cost analysis 
based on the assumption that it would be 



difficult to locate wells along fracture 
zones, where optimum yields could be 
obtained. If fracture zones can be lo- 
cated accurately on the surface and pene- 
trated with wells, then it is quite pos- 
sible that dewatering with this type of 
system could be more effective. An aver- 
age well yield of 30 gpm (1.9 L/s) was 
assumed in this analysis, but with wells 
located only in the more intensely frac- 
tured rocks, yields could average as high 
as three to four times this amount. In- 
dividual pumped wells would be cost ef- 
fective if an average well yield of 90 
to 120 gpm (5.7 to 7.6 L/s) could be 
obtained. 

The cost-effectiveness analysis did not 
consider indirect benefits of dewatering 
such as reduction of production losses 
due to high water inflows and unstable 
roofs. Production losses due to poor wa- 
ter control can be much more expensive 
than the acid drainage problems that the 
water also creates. 



60 



APPENDIX B.--CASE STUDY 2 



INTRODUCTION 

Dewatering problems are of prime con- 
cern to this mine, located in Garrett 
County, MD. The company, Met tiki Coal 
Corp. , has decided to mine roughly 9 mi 2 
(15 km 2 ) of Upper Freeport Coal. Figure 
B-l shows an aerial view of the planned 
and ongoing operations. Mining the coal 
will be quite difficult since the coal 
seam is part of the North Potomac syn- 
cline, where dips on the limbs of the 
syncline pitch up to 18°. 

The mining complex is broken up into 
three mines: the Beaver Run Mine, the 
Gobbler's Knob Mine, and the Big George 
Mine. These mines will produce both met- 
allurgical and steam coal since the qual- 
ity of the coal varies within the seam 
itself. Each mine will use four continu- 
ous miner units in conjunction with die- 
sel haulage equipment. Eventually, each 
mine will have two main sections and two 
working sections with a total projected 
production of 2 million clean tons per 
year. 

Because of the existing conditions, the 
company investigated the possibility of 
intercepting the ground water inflow to 
the mines. The company felt that better 
mining conditions could be realized in 



keeping the mines dry. They hoped that 
this would result in higher productivity. 

GEOLOGIC ENVIRONMENT 

Surface Geology 

All rocks exposed on the surface di- 
rectly above the mine are of Pennsyl- 
vanian age and belong to the Conemaugh 
Group. This formation consists of pre- 
dominantly gray and brown claystones, 
shales, siltstones, and sandstones. The 
lower part of the formation is character- 
ized by several redbeds, calcareous clay- 
stone, and fossilif erous marine shales. 

In addition to rocks , soil groups ex- 
posed on the surface include Brinkerton, 
Cookport, Gilpin, Ernest, Dekalb, and 
Stony Land. Their properties are summar- 
ized below. 

Average Permeabil- 
depth, in ity, in/h 



Brinkerton. 



Cookport, Gilpin, 
Ernest 



Dekalb, Stony Land 



50 



29-38 



24-36 



0.2-0.63 



1.6-5.1 



2.0 + 



MD 




Kempton 



LEGEND 

Proposed mine 
opening 

Proposed test-drilling 
sites, nests of 
piezometers 



II I I II Approximate area 
1 II to be undermined 



Scale, miles 
FIGURE B-l. - Planned and ongoing mine operations. 



Subsurface Geology 

A generalized stratigraphic column of 
units encountered in the subsurface is 
shown in figure B-2. All rocks in the 
subsurface are from the Conemaugh Group 
(described in the previous section) . The 
Upper Freeport Coal itself is part of the 
Allegheny Formation, which is of Pennsyl- 
vanian age. It is a relatively soft coal 
containing a shale binder 0.4 to 1.4 ft 
(12 to 0.43 m) thick near the middle of 
the seam. 

The immediate roof for the Upper Free- 
port Coal is the Uffington Shale, which 
ranges from a few inches to 10 ft (3.1 m) 
thick. This shale is, in most places, 
firm and moderately hard, but it is in- 
terbedded with soft clay near the eastern 
corner of the property. The main roof is 



61 



DEPTH, ft 
0- 



100— 



Lithlogy Description 



200— 



300- 



-:: — 



500- 



600- 



K : — 




Sandstone, shale, ond soil 

-Upper Hoffman Coalbed, 1.4 ft thick 

Sandstone ond shale 
-Lower Hoffman Coolbed, 1.9 ft thick 

Shale 
-Upper Clarysville Coalbed, 0.3 ft thick 

Shole 

Morgantown Sandstone 

Morgantown Shale 
Barton Sandstone 
-Elk Lick Coolbed, 8 ft thick 
Birmingham Shale 

Grafton Sandstone 
Ames Marine Shale 
-Harlem Coalbed, 2 ft thick 
Shale 

Jane Lew Sandstone 

Pittsburgh Shale 

-Upper Bokerstown Coalbed, 0.2 ft thick 

Soltsburg Sandstone 
-Bokerstown Coalbed, I.I to 6.I ft thick 

Meyersdale Shale 

Buffalo Sandstone 

Brush Creek Shale 
-Brush Creek Coalbed, 0.5 ft thick 
Upper Mohoning Sandstone 
Mahoning Shale 
— Mahoning Coalbed, 0.9 ft thick 
Lower Mahoning Sandstone 
Uffington Shale 

Upper Freeport Coalbed, 8 to 10 ft thick 
Bolivar Fire Cloy 



FIGURE B-2. - Generalized strat igraphic 
column, case study 2. 

Lower Mahoning Sandstone, which ranges 
from 5 to 110 ft (1.5 to 33.5 m) thick, 
and occurs 7 to 22 ft (2.1 to 6.7 m) 
above the coal. 

Total thickness of cover above the coal 
averages more than 500 ft (152 m). How- 
ever, along the southeastern edge of the 
property, at the Potomac River, the coal 
is typically about 450 ft (137 m) deep. 

The floor of Beaver Run Mine consist of 
at least 2 ft of Bolivar Fire Clay, com- 
prised of fire clay, claystone, or soft 
shale. Softest areas are confined to the 
northwest limb of the syncline. 

The principal structural feature of the 
mine property is the North Potomac syn- 
cline, which trends roughly northeast- 
southwest an average of 6,000 ft (1,829 
m) north of the North Branch of the Po- 
tomac River. The basin and southeast 
limb are relatively flat, with dips of 
0° to 3°, while dips of up to 18° exist 



near the outcrop of the Upper Freeport 
Coal on Backbone Mountain. The synclinal 
structure overlying the proposed mine is 
depicted in the schematic cross section 
(fig. B-3). 

Joints and fractures were found to have 
major trends at N 7° E, N 26° E, N 74° E, 
and N 11° W, with a minor set at N 43° E. 
No true geologic faults were detected in 
the area. 

HYDROLOGIC CONDITIONS 

Surface Water 

The mine area lies within the upper Po- 
tomac Drainage Basin, whose major river 
is the North Branch of the Potomac. This 
river also forms the southeast boundary 
of the mine area. A. number of smaller 
streams, all of which drain into the 
North Branch, are also present on the 
mine site. These include Sand Run, Lau- 
rel Run, Chestnut Ridge Run, and Red Oak 
Run. No larger bodies of water, such as 
lakes, are present on the property, al- 
though one spring is known to exist. 

Subsurface Water 

General ground water flow conditions at 
the mine sites are artesian owing, to 
the synclinal structure of the site and 
the presence of thick, impermeable shale 
units that confine existing aquifers. 

The following is a list of major aqui- 
fer units in the area: 

Thickness Feet above 
Sandstone unit range, ft coal 

Lower Mahoning.... 15-110 10 

Buffalo 15- 50 120 

Saltsburg 0-60 190 

Jane Lew 15- 25 280 

Grafton 0-40 310 

Upper Grafton 0- 20 370 

Morgantown 0- 50 470 



62 

NW. 
Backbone Mountain 



SE. 



Surface 



Potomac 
River; 







Total depth 
(Not to scale) 



7,000 ft 



FIGURE B*3. - Site cross section. 



Since 80 ft of Mahoning Shale overlie 
the Lower Mahoning Sandstone, most of the 
ground water flow into the mines will be 
from this sandstone. The Big George Mine 
differs slightly from this regime in that 
the Lower Mahoning Sandstone is almost 
entirely absent. Instead, an interbedded 
sandstone and shale unit overlies most of 
the area. This unit is extremely thick 
and less permeable than any of the indi- 
vidual aquifers. 

Permeabilities are as follows: 



Unit 

Lower Mahoning Sandstone. . 

Uffington Shale (roof 
material) 



Permeability, 
gpd/ft 2 

0.047 



.015 



Recharge 

Recharge to the Lower Mahoning Sand- 
stone, which outcrops near the north- 
ern boundary of the proposed mine site, 
and to the other aquifers above the coal 
is contingent upon infiltration from an 
average annual precipitation of 48 in 
(122 cm). Some minor infiltration may be 
expected from Sand Run, Laurel Run, and 
the North Branch of the Potomac River. 

WATER INFLOW 

Dewatering Rates Versus 
Time of Development 

Pumping rates anticipated during devel- 
opment of the mines, in million gallons 
per day, are as follows: 



63 



Walton (39) derived an alternate meth- 
od of predicting water inflows, which 
uses a variation of Darcy's law. Walton 
states: 

QM 



P = 



Aha 



(B-l) 



5 yr 10 yr 15 yr 20 yr 

Beaver Run Mine 0.38 0.94 1.6 1.7 

Gobbler's Knob Mine 83 2.7 4.1 4.9 

Big George Mine 32 .6 .88 .93 

Expected Inflow Rates The entire area of the mine was assumed 

to contribute flow either directly or in- 
directly. The entire roof area was also 
assumed to continuously contribute to in- 
flow from the moment the roof is exposed 
until the mine is eventually sealed. 

On the basis of these two assumptions, 
a baseline of equal intervals was con- 
structed across the mine area. This 
baseline roughly approximates a time line 
and can be used to extrapolate to any de- 
sired time interval. Mine advance paral- 
lel to the baseline was also assumed to 
be complete along the lateral width of 
each area. Therefore, exposed roof areas 
became the area of each mine segment 
along the baseline. This particular ar- 
rangement allows computation of inflow 
from any one segment or from the entire 
mine. 

Next, the potential head for the mine 
was determined. By definition in equa- 
tion B-l, Ah is the difference between 
the average head in the first source bed 
above the mine and the mine roof. It was 
assumed that the existing artesian system 
is, or will become, a leaky artesian sys- 
tem. Therefore, the total piezometric 
head was considered to approximate the 
ground surface. The value Ah then ap- 
proximates the thickness of the roof ma- 
terial. In the Beaver Run Mine, this 
value was calculated to be 15 ft (4.6 m) , 
and for Gobbler's Knob, it was calculated 
to be 22 ft (6.7 m) . 

The Big George Mine, however, had a 
slightly different regime. In this mine, 
the Lower Mahoning Sandstone was almost 
entirely absent. An interbedded sand- 
stone and shale unit was present over 
most of the area. This unit also is ex- 
tremely thick. Therefore, in the Big 
George Mine, the ratio of Ah to M was 
seen to approach 1. 



where P = vertical permeability of the 
confining beds, gpd/ft 2 , 

Q = quantity of water leaking 
through the roof rock, gpd, 

M = average thickness of the con- 
fining bed over the mine, 
ft, 

Ah = difference between the aver- 
age head in the first source 
bed above the mine and the 
mine roof, ft, 

and a = mine roof area through which 
leakage will occur, ft 2 . 

Consequently, any parameter can be cal- 
culated if other parameters can be deter- 
mined through prior knowledge, experi- 
mental testing, or hypotheses. In this 
case, Q, or expected inflow, was the 
quantity that was unknown and could not 
be assumed. Therefore, equation B-l can 
be rearranged to state 



Q = 



PAha 
M ' 



(B-2) 



This equation could not, however, be 
applied to all mines or even to all areas 
within a mine. Values for each mine 
were derived on a case-by-case basis. A 
knowledge of the geology of each mine was 
imperative. 



64 



Assumed permeability values were de- 
rived by reviewing existing literature on 
permeabilities and by visually inspecting 
samples of the roof shales. A value of 
0.015 gpd/ft 2 (0.071 L/s per square me- 
ter) was assumed for all calculations. 
Tables B-l, B-2, and B-3 show the com- 
pleted calculations. 

DEWATERING SCHEMES 

Dewatering in Advance of Mining 

Dewatering in advance of mining was 
considered primarily because of the high 
cost of tramming within the mine under 
wet conditions. Moisture and air convert 
the 25-ft-thick fire clay bottom into a 



gooey clay. Tramming across this type of 
floor creates deep ruts and can lead to a 
loss in productivity. Favorable condi- 
tions for dewatering in advance of mining 
were expected since the region is arte- 
sian, with most of the ground water flow 
into the mines originating from the Lower 
Mahoning Sandstone (approximately 10 ft 
above the Upper Freeport Coal). 

Test wells were drilled to evaluate 
permeability, yield, and other aquifer 
characteristics. Results showed that the 
sandstone rock unit above the Upper Free- 
port Coal is not permeable enough to 
pump. It was found to be extremely hard 
and highly fractured, resulting in ex- 
tremely poor recharge to the drilled 
wells (2 to 3 gpm, 0.13 to 0.19 L/s 



TABLE B-l. - Beaver Run inflows 





Roof 
area, ft 2 


M, 1 
ft 


Inflow 


Area 


Roof 
area, ft 2 


M, ] 
ft 


Inflow 


Area 


gpd 


Cumula- 


gpd 


Cumula- 










tive, gpd 










tive, gpd 


1... 


700,000 


15 


10,500 


10,500 


10... 


6,340,000 


15 


95,100 


940,800 


2... 


5,020,000 


13 


86,900 


97,400 


11... 


5,970,000 


12 


112,000 


1,052,800 


3... 


5,240,000 


11 


107,200 


204,600 


12... 


5,840,000 


9 


146,000 


1,198,800 


4... 


5,470,000 


13 


94,700 


299,300 


13... 


5,840,000 


7 


188,000 


1,386,800 


5... 


5,670,000 


15 


85,100 


384,400 


14... 


5,970,000 


10 


134,300 


1,521,100 


6... 


5,700,000 


14 


91,600 


476,000 


15... 


6,570,000 


13 


113,700 


1,634,800 


7... 


6,340,000 


13 


109,700 


585,700 


16... 


5,290,000 


16 


74,400 


1,709,200 


8... 


6,750,000 


12 


126,600 


712,300 


17... 


1,170,000 


17 


15,500 


1,724,700 


9... 


6,520,000 


11 


133,400 


845,700 













Im - 



M = average thickness of the confining bed over the mine. 
NOTE.— P = 0.015 gpd/ft 2 ; Ah = 15 ft. 

TABLE B-2. - Gobbler's Knob inflows 







Roof 
area, ft 2 


M, ■ 
ft 


Inflow 






Roof 
area, ft 2 


M, 1 
ft 


Inflow 


Area 


gpd 


Cumula- 
tive, gpd 


Area 


gpd 


Cumula- 
tive, gpd 


1... 
2... 
3... 
4... 
5... 
6... 
7... 
8.., 
9.. 




700,000 
4,290,000 
4,830,000 
4,830,000 
4,820,000 
4,800,000 
4,780,000 
4,760,000 
4,740,000 


11 
10 
9 
7 
6 
5 
4 
3 
4 


21,000 
142,000 
177,100 
277,700 
265,100 
316,800 
394,400 
523,600 
391,000 


21,000 

163,000 

340,100 

567,800 

832,900 

1,149,700 

1,544,100 

2,067,700 

2,458,700 


10.. 

11.. 

12.. 

13... 

14... 

15... 

16... 

17... 

18... 




4,720,000 
4,710,000 
4,690,000 
4,670,000 
4,650,000 
4,650,000 
4,100,000 
2,830,000 
2,520,000 


6 
8 
9 
7 
5 
3 
3 
4 
7 


260,000 
194,000 
172,000 
220,000 
307,000 
512,000 
451,000 
233,000 
119,000 


2,718,700 
2,912,700 
3,084,700 
3,304,700 
3,611,700 
4,123,700 
4,574,700 
4,807,700 
4,926,700 



'M 



average thickness of the confining bed over the mine. 



NOTE.— P = 0.015 gpd/ft 2 ; Ah = 22 ft. 



65 



TABLE B-3. - Big George inflows 





Roof 
area, ft 2 


Inflow 


Area 


Roof 
area, ft 2 


Inflow 


Area 


gpd 


Cumulative, 
gpd 


gpd 


Cumulative, 
gpd 


2 

3 

6 

8 


700,000 
5,270,000 
5,560,000 
5,020,000 
4,770,000 
4,510,000 
4,240,000 
4,010,000 


10,500 
79,050 
83,400 
75,300 
71,550 
67,650 
63,600 
60,150 


10,500 
89,550 
172,950 
248,250 
319,800 
387,450 
451,050 
511,200 


9 

13 


2,900,000 
2,760,000 
2,780,000 
3,560,000 
3,650,000 
3,690,000 
5,770,000 
2,620,000 


43,500 
41,400 
41,700 
53,400 
54,750 
55,350 
86,550 
39,300 


554,700 
596,100 
637,800 
691,200 
745,950 
801,300 
887,850 
927,150 



NOTE. — Assume: 



Ah 
M 



- 1; P - 0.015 gpd/ft 2 , 



maximum). These results showed that de- 
watering in advance of mining may be dif- 
ficult and expensive. 

Other factors that make dewatering in 
advance of mining impractical for this 
area are — 

• The advent of new laws (Office of 
Surface Mining, State, etc.), which state 
that if the water table or hydrologic 
balance is altered, a potable water sup- 
ply must be made available by the mining 
company to the area's landowners. 

• The natural water in the area has a 
pH of 4.0 to 4.5, which is not potable. 
By law, this water must be treated before 
being returned to the environment. 

• The mining cycle advances too rapid- 
ly for dewatering in advance of mining. 



• The cost of drilling in hard 
fractured rock is extremely high. 



and 



• The mining company has to purchase 
surface properties and acquire rights-of- 
way for access, power lines, and pipe- 
lines in the dewatering wells. The com- 
pany may also get adverse reactions from 
preservationists. 



After considering these facts, the min- 
ing company decided that dewatering in 
advance of mining would be technically, 
legally, and economically impractical. 

Dewatering During Mining 

As operations in the mine proceed down- 
dip, a number of sumps will be estab- 
lished to collect water. The water will 
be pumped in three stages. Face pumps 
will transfer water collected at the face 
to a main sump, where it will be picked 
up and pumped out of the mine. 

In approximately 10 yr, the operations 
will reach the base of the North Potomac 
syncline, where it is anticipated that 
wells will be drilled from the surface to 
main sump areas located at the syncline 
base. All subsequent dewatering will be 
accomplished through staged pumping. 

The mining operations should have ex- 
cellent control over water infiltration 
since the majority of the mine life will 
be spent advancing downdip. This, in 
conjunction with the practice of segre- 
gating flows and minimizing contact with 
pyritic materials, will minimize mine 
water contamination. 



66 



APPENDIX C.--CASE STUDY 3 



INTRODUCTION 

The mine used in the third case study 
has had a history of water problems. The 
Nemacolin Mine, owned by Jones and Laugh- 
lin Steel Corp. and located near Nemaco- 
lin, PA, has a total area of 11,000 acres 
(4,452 hectares), which generate roughly 
2 million gpd (7.6 million L/d) of water. 
Many of the smaller areas within the mine 
generate between 200 and 300 gpm (12.6 to 
18.9 L/s). 

The Pittsburgh Coal of the Monongahela 
Group is the only seam mined. The coal 
seam averages 8 ft (0.24 m) in thickness 
and is located at depths ranging from 160 
to 540 ft (48.8 to 164.7 m) . For the 
most part, the seam is more than 400 ft 
(122 m) deep. 

Most of this mine has been excavated. 
Only a small area of about 1-1/4 mi 2 
(3.24 km 2 ) has remained unmined. This 
area is bounded by Muddy Creek on one 
side, the Monongahela River on another, 
and by worked-out sections on a third 
side (figure 6 in the main text). Con- 
siderable water was generated by the ad- 
vancement of operations into this area. 
The amount of water currently being 
generated is so great that if left un- 
checked, the company would be forced to 
shut down the operation. This has caused 
the company to consider changes in the 
mining and water-collecting plan to re- 
duce the water inflow. 



belong either to the Dunkard or Mononga- 
hela Groups. The formations exposed are 
the Waynesburg, the Uniontown, and the 
upper member of the Pittsburgh Formation. 
The Waynesburg and Uniontown Formations 
consists of thinly to thickly bedded 
sandstone, shales, siltstones, and mud- 
stones, with numerous interbeds of car- 
bonaceous shale, argillaceous limestone, 
and coal. Clays tone and limestone are 
found less frequently. These coalbeds 
occur in the Waynesburg Formation; the 
thickest is located at the base in two 
and, locally, three benches separated by 
layers of claystone. This coalbed is 50 
to 80 in (1.27 to 2.03 m) thick. An im- 
pure coalbed of less than 1 ft (0.31 m) 
marks the base of the Uniontown Formation 
(Uniontown Coalbed). In contrast, the 
upper member of the Pittsburgh Formation 
consists of four distinct units of argil- 
laceous limestone separated by muds tone, 
siltstone, and sandstone units of charac- 
teristic greenish-gray color. 

All rocks in the subsurface are from 
the Upper Pennsylvanian and the Lower 
Permian periods. They can be divided in- 
to two groups : the Monongahela and the 
Dunkard. These consist predominantly of 
interbedded limestone, mudstone, shale, 
and sandstone. The commercially mined 
coal bed, the Pittsburgh Coal, is 60 to 
90 in (1.52 to 2.29 m) thick. 

The slope of the bed does not exceed a 
half degree over extensive areas. 



GEOLOGIC ENVIRONMENT 



HYDROLOGIC CONDITIONS 



Quaternary alluvium consisting of un- 
consolidated silt, sand, gravel, and cob- 
bles is found in, and adjacent to, Muddy 
Creek and the Monongahela River. Gener- 
ally, unconsolidated and poorly sorted 
alluvium composing the Carmichaels Forma- 
tion is found in ancient, abandoned river 
channels and on rock terraces related to 
this ancient drainage network. These de- 
posits consist of laminated clay, mixed 
yellowish-brown clay, silt, sand, and 
well-rounded pebbles , cobbles , and boul- 
ders of sandstone. 

All rocks exposed on the surface are of 
Upper Pennsylvanian and Permian age and 



Surface Water 

The active mine area is bounded on the 
west by Muddy Creek and on the northeast, 
east, and southeast by the Monongahela 
River. At the most northern point of the 
mine area, Muddy Creek flows into the 
Monongahela River. In addition, the mine 
property has a number of intermittent 
streams, which flow into either the Mon- 
ongahela River or Muddy Creek. 

Springs of variable flows, which yield 
a few gallons per minute, are numerous 
along the outcrops of the Lower Limestone 
Member of the Uniontown Formation. Many 



67 



of these springs are true joint or bed- 
ding plane springs supplied by a distant 
source and are an indication of the 
water-yielding capacity of the beds. 
Others, those springs whose flows are 
most variable, presumably originate lo- 
cally in vadose water trapped above one 
of the impermeable limestone beds. Such 
springs are not indicative of the water- 
yielding capacity of the beds. 

Ground Water Conditions 



The Waynesburg Sandstone and the Pitts- 
burgh Sandstone are the principal water- 
bearing zones of the area. There are a 
number of other water-bearing zones that 
yield limited supplies of ground water 
from bedding plane conduits. Although 
they are not deeply buried, they are im- 
permeable beneath continuous cover. In 
addition, small perched water zones pro- 
vide small supplies of water. 

The Waynesburg Sandstone is 20 to 60 ft 
(6.1 to 18.3 m) thick and is commonly 
more than 40 ft (12.2 m) thick. The unit 
is light gray or buff, micaceous, and 
usually arkosic or feldspathic. 

The upper division is typically cross- 
bedded and flaggy, although the lower 
division is generally massive and fri- 
able and locally coarse grained or even 
pebbly. The lower division is a bluff 
maker, and in many places its outcrops 
are somewhat cavernous. 

The Waynesburg Sandstone, especially 
the massive and coarser grained lower 
portion, is by far the outstanding water- 
bearing member of the entire Permian se- 
ries and has been extensively developed. 

The coarser facies of the member yield 
as much as 65 gpm (4.1 L/s) where the 
member lies below drainage level. The 
specific yield of individual wells is not 
known precisely but is approximately 2 
gpm (0.13 L/s) for each foot of drawdown 
in wells at the town of Waynesburg lo- 
cated about 10 miles west of the mine. 
Water is confined within the member under 
moderate hydrostatic pressure. It is 
noteworthy that wells reported to have 
been drilled to a depth of 200 ft (61 ra) 
at the flour mill and at the electric 
light plant at Waynesburg failed to ob- 
tain water, although borings of that 



depth should have penetrated the Waynes- 
burg Sandstone. This reported phenomenon 
has never been observed with the Waynes- 
burg Sandstone elsewhere, and if authen- 
tic, points to considerable variations in 
permeability of the member from place to 
place. 

The interval between the Redstone and 
Pittsburgh Coals is in many places occu- 
pied entirely or partially by the Pitts- 
burgh Sandstone, which has been called 
the Upper Pittsburgh. This bed is typi- 
cally coarse grained, massive to irregu- 
larly bedded, friable, and buff to dark 
gray or brown in color. In many local- 
ities, however, it grades laterally into 
flaggy or thin-bedded sandstone and into 
interbedded sandy shales and sandstone 
lentils. The Pittsburgh Sandstone ranges 
in thickness from to 70 ft (0 to 21.3 
m) and generally thickens toward the 
south. 

The Pittsburgh Sandstone and its equiv- 
alents are highly permeable over wide 
areas, but they have been drained wherev- 
er the underlying Pittsburgh Coal has 
been mined and the roofs above the aban- 
doned mine entries have collapsed. Con- 
sequently, this sandstone is no longer a 
potential source of water in many of the 
mining districts, especially in those 
that have long been worked out and aban- 
doned. Furthermore, such drainage is 
likely to become more extensive in the 
future. In some places, the muddy water 
that percolates down from the surface 
along the larger subsidence fractures or 
"breaks" fills the drainage conduits so 
that the sandstone may become water bear- 
ing again after a lapse of several years. 
It is quite by chance, however, that such 
puddling takes place, and in most dis- 
tricts the water-yielding capacity of the 
sandstone is never fully restored. The 
member displays its normal water-bearing 
properties in those districts in which 
the coal has not been mined. In many 
mining districts there has been very lit- 
tle roof collapse and the member has not 
been completely drained. In these cases, 
wells of moderate yield may be obtained 
if care is taken to cease drilling be- 
fore the well penetrates the mine entry. 
Where the member lies below drainage lev- 
el, it is likely to be saturated, have a 



68 



moderately high head, and a moderately 
large yield. Yields range from to 35 
gpm (0 to 2.2 L/s), the maximum being at- 
tained where the member lies below drain- 
age level on the flanks of a syncline. 

WATER INFLOW 

Rate 

The amount of water entering the whole 
mining operation on any given day has 
been estimated to be roughly 2 million 
gpd (7.6 million L/d). Small areas with- 
in the mine experience inflows of 200 to 
300 gpm (12.6 to 18.9 L/s). In the one 
active section, most of the water is gen- 
erated during the advance cycle of mine 
development, causing a considerable num- 
ber of problems in production and mine 
development. In addition, roof bolt 
holes have yielded up to 50 gpm (3.2 L/s) 
of water in many instances. 

Most of this water is found along the 
contact between the Pittsburgh Sandstone 
and a shale complex that lies directly 
above the Pittsburgh Coal Seam. The 
shale complex consists of an 8-in (0.2-m) 
coal seam sandwiched between two 2-in 
(0.05-m) shale beds. The water is held 
under considerable head; sprays of up to 
4 ft (1.22 m) from the contact have been 
observed. 

Water also enters the mine through cer- 
tain fracture traces; however, their flow 
is not constant. 

Source 

Most of the water enters the mine 
through the roof and exterior faces. 
This water is transmitted primarily by 
bedding planes and roof bolt holes. A 
considerably smaller percentage seeps 
through fractures and through barrier 
pillars that separate abandoned parts of 
the mine from the active sections. 

The source of the water infiltrating 
the mine has not yet been fully deter- 
mined. Observations show that water is 
entering the active section along the 
base of the Pittsburgh Sandstone. Al- 
though this sandstone is a water sup- 
plier, it is not capable of supplying 300 



gpm (18.9 L/s) of water. Water wells in 
the sandstone yield only up to 35 gpm 
(2.2 L/s), and this is only under the 
most optimal conditions. In contrast, 
roof bolt holes have yielded up to 50 gpm 
(3.2 L/s). In addition to this, raining 
operations have experienced considerable 
problems in the areas closest to the Mon- 
ongahela River. 

Based on these observations, it is be- 
lieved that most of the water is origi- 
nating from the Monongahela River. The 
water is moving along the permeable bed- 
ding planes and is entering the mine at 
the point where the mine operations in- 
tersect these planes. 

DEWATERING SCHEME 

The dewatering scheme in the active 
section of the underground mine complex 
first consisted of a conventional series 
of sumps with pumps transporting the 
water to main sumps where it was then 
pumped out of the mine. This system 
proved to be inadequate since the inflow 
was so great that it disrupted face oper- 
ations. As a consequence, mine engineers 
thought that the water inflow could be 
decreased by changing the direction of 
mining by 90°. This had only limited 
success . 

Since most of the water flowing into 
the mines was coming from the direction 
of the Monongahela River, mine engineers 
decided that in order to prevent disrup- 
tion of face operations, the water would 
have to be intercepted before it reached 
the face. This technique is currently 
being implemented by second-mining the 
part of the operation closest to the Mon- 
ongahela River, thereby creating a huge 
sump. It is hoped that the water will 
drain into the sump before reaching the 
face. The water in the sump will then be 
pumped out of the mine. This system is a 
modification of the gravity drainage and 
mine pumping system to dewater above a 
mine. Instead of using drilled holes to 
collect water, the water is collected by 
fracturing the confining bed and part of 
the source bed so that the water will run 
along the fractures into the mine. 



izU.S. GPO: 1985-505-019/20,062 



INT.-BU.OF MIN ES,PGH.,P A. 27979 



X83 * 



\3 *0. A * A 

.>■"»* **b j> 6 <• "! ° 












'^6" 
















,v^ 'IS; > V *V : 



■4 o>. 








4 0^ 






*b^ 







4? -^ 




,/ ^••^'/ ^/^ f \/ °^^^/ %^-\^ °<^^^/ 








^°^ 








V .*i^L'*. <^ 




^ 











^ '*^« # A,© V 




^° A 





4T ^ 



« t '- s * "^b, a> v c'1% "5>* 










°^ 




'\^ 




4 ^ . 









c. <p 








O N " A' 

v* .•Jm^:* '<^ a? v 




'o? 











6** 



\J. *o. »* A <» 






,* v % 








0* ^X_:+o 



^^ 













!>** 

^ 



v-cr 



;- "-w 



v^ \'^>\/* %^^%c/ %/*^V* \^^v* 






jfe \/ ^ ^ ;jg&. \/ ;|te-. %/ : 



■J ^ ; JI 










^, p •&„ A 



^ 






of 



c "' 



LIBRARY OF CONGRESS 
ll'illlllNIIIIIH'li 



002 955 964 8 



